Cleanup narrowing warning in pin_is_protected

Marlin/src/HAL/HAL_LPC1768/pinmapping.cpp

 #include "../../gcode/parser.h"
 
 // Get the digital pin for an analog index
-pin_t analogInputToDigitalPin(const uint8_t p) {
-  return (p < COUNT(adc_pin_table) ? adc_pin_table[p] : P_NC);
+pin_t analogInputToDigitalPin(const int8_t p) {
+  return (WITHIN(p, 0, NUM_ANALOG_INPUTS) ? adc_pin_table[p] : P_NC);
 }
 
 // Return the index of a pin number

Marlin/src/HAL/HAL_LPC1768/pinmapping.h

   P_NC,  P_NC,  P_NC,  P_NC,  P4_28, P4_29, P_NC,  P_NC
 };
 
-constexpr int16_t NUM_DIGITAL_PINS = COUNT(pin_map);
+constexpr int8_t NUM_DIGITAL_PINS = COUNT(pin_map);
 
 constexpr pin_t adc_pin_table[] = {
   P0_23, P0_24, P0_25, P0_26, P1_30, P1_31,
 #define HAL_SENSITIVE_PINS P0_06, P0_07, P0_08, P0_09, P0_29, P0_30
 
 // Get the digital pin for an analog index
-pin_t analogInputToDigitalPin(const uint8_t p);
+pin_t analogInputToDigitalPin(const int8_t p);
 
 // Return the index of a pin number
 // The pin number given here is in the form ppp:nnnnn

Marlin/src/pins/pins.h

   #define MAX_EXTRUDERS 5
 #endif
 
-// Marlin needs to account for pins that equal -1
-#define marlinAnalogInputToDigitalPin(p) ((p) == -1 ? -1 : analogInputToDigitalPin(p))
-
 //
 // Assign auto fan pins if needed
 //
   #endif // EXTRUDERS > 2
 #endif // EXTRUDERS > 1
 
-#define _H0_PINS HEATER_0_PIN, E0_AUTO_FAN_PIN, marlinAnalogInputToDigitalPin(TEMP_0_PIN),
+#define _H0_PINS HEATER_0_PIN, E0_AUTO_FAN_PIN, analogInputToDigitalPin(TEMP_0_PIN),
 #define _H1_PINS
 #define _H2_PINS
 #define _H3_PINS
 
 #if HOTENDS > 1
   #undef _H1_PINS
-  #define _H1_PINS HEATER_1_PIN, E1_AUTO_FAN_PIN, marlinAnalogInputToDigitalPin(TEMP_1_PIN),
+  #define _H1_PINS HEATER_1_PIN, E1_AUTO_FAN_PIN, analogInputToDigitalPin(TEMP_1_PIN),
   #if HOTENDS > 2
     #undef _H2_PINS
-    #define _H2_PINS HEATER_2_PIN, E2_AUTO_FAN_PIN, marlinAnalogInputToDigitalPin(TEMP_2_PIN),
+    #define _H2_PINS HEATER_2_PIN, E2_AUTO_FAN_PIN, analogInputToDigitalPin(TEMP_2_PIN),
     #if HOTENDS > 3
       #undef _H3_PINS
-      #define _H3_PINS HEATER_3_PIN, E3_AUTO_FAN_PIN, marlinAnalogInputToDigitalPin(TEMP_3_PIN),
+      #define _H3_PINS HEATER_3_PIN, E3_AUTO_FAN_PIN, analogInputToDigitalPin(TEMP_3_PIN),
       #if HOTENDS > 4
         #undef _H4_PINS
-        #define _H4_PINS HEATER_4_PIN, marlinAnalogInputToDigitalPin(TEMP_4_PIN),
+        #define _H4_PINS HEATER_4_PIN, analogInputToDigitalPin(TEMP_4_PIN),
       #endif // HOTENDS > 4
     #endif // HOTENDS > 3
   #endif // HOTENDS > 2
   #endif // MIXING_STEPPERS > 2
 #endif // MIXING_STEPPERS > 1
 
-#define BED_PINS HEATER_BED_PIN, marlinAnalogInputToDigitalPin(TEMP_BED_PIN),
+#define BED_PINS HEATER_BED_PIN, analogInputToDigitalPin(TEMP_BED_PIN),
 
 //
 // Assign endstop pins for boards with only 3 connectors