clear out interrupt when freeing the timer

Closes #5418

Author: jepler

ports/raspberrypi/common-hal/rgbmatrix/RGBMatrix.c

@@ -33,6 +33,7 @@
 #include "shared-module/rgbmatrix/RGBMatrix.h"
 
 #include "src/rp2_common/hardware_pwm/include/hardware/pwm.h"
+#include "src/rp2_common/hardware_irq/include/hardware/irq.h"
 
 void *common_hal_rgbmatrix_timer_allocate(rgbmatrix_rgbmatrix_obj_t *self) {
     // Choose a PWM channel based on the first RGB pin
@@ -65,6 +66,8 @@ void common_hal_rgbmatrix_timer_free(void *ptr) {
     uint8_t slice = value & 0xff;
     uint8_t channel = value >> 8;
     pwm_set_enabled(slice, false);
+    irq_set_enabled(PWM_IRQ_WRAP, false);
+    pwm_clear_irq(slice);
     pwmout_free(slice, channel);
     return;
 }