Rename SPI class to avoid conflict (good?)

Marlin/src/libs/private_spi.h

 #include <stdint.h>
 
 template<uint8_t MisoPin, uint8_t MosiPin, uint8_t SckPin>
-class SPI {
+class SPIclass {
   static SoftSPI<MisoPin, MosiPin, SckPin> softSPI;
   public:
     FORCE_INLINE static void init() { softSPI.begin(); }
 
 // Hardware SPI
 template<>
-class SPI<MISO_PIN, MOSI_PIN, SCK_PIN> {
+class SPIclass<MISO_PIN, MOSI_PIN, SCK_PIN> {
   public:
     FORCE_INLINE static void init() {
         OUT_WRITE(SCK_PIN, LOW);

Marlin/src/module/temperature.cpp

   #ifndef MAX6675_DO_PIN
     #define MAX6675_DO_PIN MISO_PIN
   #endif
-  SPI<MAX6675_DO_PIN, MOSI_PIN, MAX6675_SCK_PIN> max6675_spi;
+  SPIclass<MAX6675_DO_PIN, MOSI_PIN, MAX6675_SCK_PIN> max6675_spi;
 #endif
 
 /**