Fix external pin interrupt definitions for Feather M4

Spent a while trying to figure out why analog pins A4/18 and A5/19 where not working as interrupts, turns out the external interrupt definitions are wrong in-code. These fixed definitions now match the published pinout diagram for the feather m4 and the samd51 datasheet.

Author: NanoCodeBug

variants/feather_m4/variant.cpp

@@ -62,8 +62,8 @@ const PinDescription g_APinDescription[]=
   { PORTA,  5, PIO_ANALOG, PIN_ATTR_ANALOG, ADC_Channel5, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_5 },
   { PORTB,  8, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel2, TC4_CH0, TC4_CH0, EXTERNAL_INT_8 },
   { PORTB,  9, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel3, TC4_CH1, TC4_CH1, EXTERNAL_INT_9 },
-  { PORTA,  4, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel4, TC0_CH0, TC0_CH0, EXTERNAL_INT_6 },
-  { PORTA,  6, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel6, TC1_CH0, TC1_CH0, EXTERNAL_INT_10 },
+  { PORTA,  4, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel4, TC0_CH0, TC0_CH0, EXTERNAL_INT_4 },
+  { PORTA,  6, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel6, TC1_CH0, TC1_CH0, EXTERNAL_INT_6 },
 
   // A6, D20 - VDiv!
   { PORTB,  1, PIO_ANALOG, PIN_ATTR_ANALOG, ADC_Channel13, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_1 },