Fix SAMD51 timer usage (#17471)

Marlin/src/HAL/SAMD51/Servo.cpp

@@ -55,7 +55,7 @@
 static volatile int8_t currentServoIndex[_Nbr_16timers];    // index for the servo being pulsed for each timer (or -1 if refresh interval)
 
 FORCE_INLINE static uint16_t getTimerCount() {
-  Tc * const tc = TimerConfig[SERVO_TC].pTimer;
+  Tc * const tc = TimerConfig[SERVO_TC].pTc;
 
   tc->COUNT16.CTRLBSET.reg = TC_CTRLBCLR_CMD_READSYNC;
   SYNC(tc->COUNT16.SYNCBUSY.bit.CTRLB || tc->COUNT16.SYNCBUSY.bit.COUNT);
@@ -67,7 +67,7 @@ FORCE_INLINE static uint16_t getTimerCount() {
 // Interrupt handler for the TC
 // ----------------------------
 HAL_SERVO_TIMER_ISR() {
-  Tc * const tc = TimerConfig[SERVO_TC].pTimer;
+  Tc * const tc = TimerConfig[SERVO_TC].pTc;
   const timer16_Sequence_t timer =
     #ifndef _useTimer1
       _timer2
@@ -127,7 +127,7 @@ HAL_SERVO_TIMER_ISR() {
 }
 
 void initISR(timer16_Sequence_t timer) {
-  Tc * const tc = TimerConfig[SERVO_TC].pTimer;
+  Tc * const tc = TimerConfig[SERVO_TC].pTc;
   const uint8_t tcChannel = TIMER_TCCHANNEL(timer);
 
   static bool initialized = false;  // Servo TC has been initialized
@@ -204,7 +204,7 @@ void initISR(timer16_Sequence_t timer) {
 }
 
 void finISR(timer16_Sequence_t timer) {
-  Tc * const tc = TimerConfig[SERVO_TC].pTimer;
+  Tc * const tc = TimerConfig[SERVO_TC].pTc;
   const uint8_t tcChannel = TIMER_TCCHANNEL(timer);
 
   // Disable the match channel interrupt request

Marlin/src/HAL/SAMD51/inc/SanityCheck.h

@@ -35,6 +35,10 @@
   #error "OnBoard SPI BUS can't be shared with other devices."
 #endif
 
+#if SERVO_TC == RTC_TIMER_NUM
+  #error "Servos can't use RTC timer"
+#endif
+
 #if ENABLED(EMERGENCY_PARSER)
   #error "EMERGENCY_PARSER is not yet implemented for SAMD51. Disable EMERGENCY_PARSER to continue."
 #endif