Apply #pragma once, misc cleanup (#12322)

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

Marlin/src/HAL/shared/HAL_SPI.h

@@ -19,15 +19,13 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * HAL/HAL_SPI.h
  * Core Marlin definitions for SPI, implemented in the HALs
  */
 
-#ifndef _HAL_SPI_H_
-#define _HAL_SPI_H_
-
 #include <stdint.h>
 
 /**
@@ -78,5 +76,3 @@ void spiRead(uint8_t* buf, uint16_t nbyte);
 void spiSendBlock(uint8_t token, const uint8_t* buf);
 /** Begin SPI transaction, set clock, bit order, data mode */
 void spiBeginTransaction(uint32_t spiClock, uint8_t bitOrder, uint8_t dataMode);
-
-#endif // _HAL_SPI_H_