Apply #pragma once, misc cleanup (#12322)

* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Marlin/src/feature/leds/neopixel.h

@@ -19,14 +19,12 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * Neopixel support
  */
 
-#ifndef __NEOPIXEL_H__
-#define __NEOPIXEL_H__
-
 #include "../../inc/MarlinConfig.h"
 
 #include <Adafruit_NeoPixel.h>
@@ -46,5 +44,3 @@ void set_neopixel_color(const uint32_t color);
 //bool neopixel_set_led_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t w, const uint8_t p);
 
 extern Adafruit_NeoPixel pixels;
-
-#endif // __NEOPIXEL_H__