Fix PLR/M43 warnings (#14333)

Marlin/src/HAL/HAL_STM32F1/HAL_Servo_STM32F1.cpp

   if (!PWM_PIN(pin)) return false;
 
   timer_dev *tdev = PIN_MAP[pin].timer_device;
-  uint8_t tchan = PIN_MAP[pin].timer_channel;
+  //uint8_t tchan = PIN_MAP[pin].timer_channel;
 
   SET_PWM(pin);
   servoWrite(pin, 0);
 
 #else
 
-  bool libServo::setupSoftPWM(const int32_t pin) {}
+  bool libServo::setupSoftPWM(const int32_t pin) { return false; }
   void libServo::pwmSetDuty(const uint16_t duty_cycle) {}
   void libServo::pauseSoftPWM() {}
 

Marlin/src/feature/power_loss_recovery.cpp

   // Pretend that all axes are homed
   axis_homed = axis_known_position = xyz_bits;
 
-  char cmd[50], str_1[16], str_2[16];
+  char cmd[MAX_CMD_SIZE+16], str_1[16], str_2[16];
 
   // Select the previously active tool (with no_move)
   #if EXTRUDERS > 1

Marlin/src/gcode/config/M43.cpp

                       ", stow angle:   ", servo_angles[probe_index][1]
     );
 
-    bool deploy_state, stow_state;
+    bool deploy_state = false, stow_state;
 
     #if ENABLED(Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN)