SAMD51: More reliable Servo/BLTouch PWM (#18710)

Marlin/src/HAL/SAMD51/timers.cpp

 // --------------------------------------------------------------------------
 // Includes
 // --------------------------------------------------------------------------
+
 #include "../../inc/MarlinConfig.h"
+#include "ServoTimers.h" // for SERVO_TC
 
 // --------------------------------------------------------------------------
 // Local defines
   { {.pTc=TC0},  TC0_IRQn, TC_PRIORITY(0) },  // 0 - stepper (assigned priority 2)
   { {.pTc=TC1},  TC1_IRQn, TC_PRIORITY(1) },  // 1 - stepper (needed by 32 bit timers)
   { {.pTc=TC2},  TC2_IRQn, 5              },  // 2 - tone (reserved by framework and fixed assigned priority 5)
-  { {.pTc=TC3},  TC3_IRQn, TC_PRIORITY(3) },  // 3 - servo (no interrupts used)
+  { {.pTc=TC3},  TC3_IRQn, TC_PRIORITY(3) },  // 3 - servo (assigned priority 1)
   { {.pTc=TC4},  TC4_IRQn, TC_PRIORITY(4) },  // 4 - software serial (no interrupts used)
   { {.pTc=TC5},  TC5_IRQn, TC_PRIORITY(5) },
   { {.pTc=TC6},  TC6_IRQn, TC_PRIORITY(6) },

Marlin/src/HAL/SAMD51/timers.h

 #define ENABLE_TEMPERATURE_INTERRUPT()  HAL_timer_enable_interrupt(TEMP_TIMER_NUM)
 #define DISABLE_TEMPERATURE_INTERRUPT() HAL_timer_disable_interrupt(TEMP_TIMER_NUM)
 
-#define TC_PRIORITY(t)        (t == STEP_TIMER_NUM || t == PULSE_TIMER_NUM) ? 2   \
-                               : (t == TEMP_TIMER_NUM) ? 6                        \
+#define TC_PRIORITY(t)        t == SERVO_TC ? 1                                     \
+                               : (t == STEP_TIMER_NUM || t == PULSE_TIMER_NUM) ? 2  \
+                               : (t == TEMP_TIMER_NUM) ? 6                          \
                                : 7
 
 #define _TC_HANDLER(t)          void TC##t##_Handler()