T4 fix typo in HardwareSerial

rx_pins should depend on cnt_rx_pins not cnt_tx_pins, currentlty the same so does not impact

teensy4/HardwareSerial.h

 		void (*serial_event_handler_check)(void);
 		volatile uint32_t &ccm_register;
 		const uint32_t ccm_value;
-		pin_info_t rx_pins[cnt_tx_pins];
+		pin_info_t rx_pins[cnt_rx_pins];
 		pin_info_t tx_pins[cnt_tx_pins];
 		const uint8_t cts_pin;
 		const uint8_t cts_mux_val;