T4.x CTS pins - T4.1 add memory chip area to Serial ports.

A few of the T4 and now T4.1 Serial ports support a CTS pin.  One was previous fixed, added the others to tables.

Also T4.1 has Some Serial port pins in the area that the optional memory chips could be installed

teensy4/HardwareSerial1.cpp

 const HardwareSerial::hardware_t UART6_Hardware = {
 	0, IRQ_LPUART6, &IRQHandler_Serial1, &serial_event_check_serial1,
 	CCM_CCGR3, CCM_CCGR3_LPUART6(CCM_CCGR_ON),
+	#if defined(ARDUINO_TEENSY41)
+	{{0,2, &IOMUXC_LPUART6_RX_SELECT_INPUT, 1}, {52, 2, &IOMUXC_LPUART6_RX_SELECT_INPUT, 0}},
+	{{1,2, &IOMUXC_LPUART6_TX_SELECT_INPUT, 0}, {53, 2, nullptr, 0}},
+	#else
 	{{0,2, &IOMUXC_LPUART6_RX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
-	{{1,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
+	{{1,2, &IOMUXC_LPUART6_TX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
+	#endif
 	0xff, // No CTS pin
 	0, // No CTS
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark

teensy4/HardwareSerial2.cpp

 	{{7,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
 	#elif defined(__IMXRT1062__)
 	{{7,2, &IOMUXC_LPUART4_RX_SELECT_INPUT, 2}, {0xff, 0xff, nullptr, 0}},
-	{{8,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
+	{{8,2, &IOMUXC_LPUART4_TX_SELECT_INPUT, 2}, {0xff, 0xff, nullptr, 0}},
 	#endif
 	0xff, // No CTS pin
 	0, // No CTS

teensy4/HardwareSerial3.cpp

 	2, IRQ_LPUART2, &IRQHandler_Serial3, &serial_event_check_serial3, 
 	CCM_CCGR0, CCM_CCGR0_LPUART2(CCM_CCGR_ON),
 	{{15,2, &IOMUXC_LPUART2_RX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
-	{{14,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
+	{{14,2, &IOMUXC_LPUART2_TX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
 	19, //IOMUXC_SW_MUX_CTL_PAD_GPIO_AD_B1_00, // 19
 	2, // page 473 
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark

teensy4/HardwareSerial4.cpp

 	3, IRQ_LPUART3, &IRQHandler_Serial4, &serial_event_check_serial4,
 	CCM_CCGR0, CCM_CCGR0_LPUART3(CCM_CCGR_ON),
 	{{16,2, &IOMUXC_LPUART3_RX_SELECT_INPUT, 0}, {0xff, 0xff, nullptr, 0}},
-	{{17,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
+	{{17,2, &IOMUXC_LPUART3_TX_SELECT_INPUT, 0}, {0xff, 0xff, nullptr, 0}},
 	0xff, // No CTS pin
 	0, // No CTS
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark

teensy4/HardwareSerial5.cpp

 	#if defined(ARDUINO_TEENSY41)
 	{{21,2, &IOMUXC_LPUART8_RX_SELECT_INPUT, 1}, {46, 2, &IOMUXC_LPUART8_RX_SELECT_INPUT, 0}},
 	{{20,2, &IOMUXC_LPUART8_TX_SELECT_INPUT, 1}, {47, 2, &IOMUXC_LPUART8_TX_SELECT_INPUT, 0}},
+	43, //  CTS pin
+	2, //  CTS
 	#else
 	{{21,2, &IOMUXC_LPUART8_RX_SELECT_INPUT, 1}, {38, 2, &IOMUXC_LPUART8_RX_SELECT_INPUT, 0}},
 	{{20,2, &IOMUXC_LPUART8_TX_SELECT_INPUT, 1}, {39, 2, &IOMUXC_LPUART8_TX_SELECT_INPUT, 0}},
+	35, //  CTS pin
+	2, //  CTS
 	#endif
-	0xff, // No CTS pin
-	0, // No CTS
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark
 };
 HardwareSerial Serial5(&IMXRT_LPUART8, &UART8_Hardware, tx_buffer5, SERIAL5_TX_BUFFER_SIZE,

teensy4/HardwareSerial7.cpp

 	6, IRQ_LPUART7, &IRQHandler_Serial7, &serial_event_check_serial7,
 	CCM_CCGR5, CCM_CCGR5_LPUART7(CCM_CCGR_ON),
 	{{28,2, &IOMUXC_LPUART7_RX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
-	{{29,2, nullptr, 0}, {0xff, 0xff, nullptr, 0}},
+	{{29,2, &IOMUXC_LPUART7_TX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
 	0xff, // No CTS pin
 	0, // No CTS
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark

teensy4/HardwareSerial8.cpp

 static HardwareSerial::hardware_t UART5_Hardware = {
 	7, IRQ_LPUART5, &IRQHandler_Serial8, &serial_event_check_serial8,
 	CCM_CCGR3, CCM_CCGR3_LPUART5(CCM_CCGR_ON),
-    {{34,1, &IOMUXC_LPUART5_RX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
+    {{34,1, &IOMUXC_LPUART5_RX_SELECT_INPUT, 1}, {48, 2, &IOMUXC_LPUART5_RX_SELECT_INPUT, 0}},
     {{35,1, &IOMUXC_LPUART5_TX_SELECT_INPUT, 1}, {0xff, 0xff, nullptr, 0}},
 
-	0xff, // No CTS pin
-	0, // No CTS
+	50, // CTS pin
+	2, //  CTS
 	IRQ_PRIORITY, 38, 24, // IRQ, rts_low_watermark, rts_high_watermark
 };
 HardwareSerial Serial8(&IMXRT_LPUART5, &UART5_Hardware, tx_buffer8, SERIAL8_TX_BUFFER_SIZE,