Don't allow pre-init of Serial2 Teensy 3.2 pins on Teensy3.6

teensy3/serial2.c

 #if defined(KINETISK)
 	switch (rx_pin_num) {
 		case 9: CORE_PIN9_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(3); break;
+		#if defined(__MK20DX128__) || defined(__MK20DX256__)    // T3.0, T3.1, T3.2
 		case 26: CORE_PIN26_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(3); break;
-		#if defined(__MK64FX512__) || defined(__MK66FX1M0__)  // on T3.5 or T3.6
+		#elif defined(__MK64FX512__) || defined(__MK66FX1M0__)  // T3.5 or T3.6
 		case 59: CORE_PIN59_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(3); break;
 		#endif
 	}
 	switch (tx_pin_num) {
 		case 10: CORE_PIN10_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
+		#if defined(__MK20DX128__) || defined(__MK20DX256__)    // T3.0, T3.1, T3.2
 		case 31: CORE_PIN31_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
-		#if defined(__MK64FX512__) || defined(__MK66FX1M0__)  // on T3.5 or T3.6
+		#elif defined(__MK64FX512__) || defined(__MK66FX1M0__)  // T3.5 or T3.6
 		case 58: CORE_PIN58_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
 		#endif
 	}