ld_pwr_exc_protector: set smpr to be slowest

- reduce noise on the analog watchdog

src/laser_diode/ld_pwr_exc_protector.rs

@@ -125,9 +125,10 @@ impl LdPwrExcProtector {
         });
         // Set the Conversion Sequence to include Pd Mon Pin
         pac_adc.sqr3.write(|w| w.sq1().variant(PD_MON_ADC_CH_ID));
-        // Set all sampling channels to have fastest sampling interval
-        pac_adc.smpr1.reset();
-        pac_adc.smpr2.reset();
+
+        // Set all sampling channels to have slowest sampling interval
+        pac_adc.smpr1.write(|w| unsafe { w.bits(0xFFFF) });
+        pac_adc.smpr2.write(|w| unsafe { w.bits(0xFFFF) });
 
         // Set the higher threshold to be max value initially
         pac_adc.htr.write(|w| w.ht().variant(MAX_SAMPLE));