Add pin 24 & 25 to Teensy LC serial_begin()

teensy3/serial1.c

 		case 21: CORE_PIN21_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(3); break;
 		#if defined(KINETISL)
 		case 3:  CORE_PIN3_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(2); break;
+		case 25: CORE_PIN25_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(4); break;
 		#endif
 		#if defined(__MK64FX512__) || defined(__MK66FX1M0__)
 		case 27: CORE_PIN27_CONFIG = PORT_PCR_PE | PORT_PCR_PS | PORT_PCR_PFE | PORT_PCR_MUX(3); break;
 		case 5:  CORE_PIN5_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
 		#if defined(KINETISL)
 		case 4:  CORE_PIN4_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(2); break;
+		case 24: CORE_PIN24_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(4); break;
 		#endif
 		#if defined(__MK64FX512__) || defined(__MK66FX1M0__)
 		case 26: CORE_PIN26_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;