SPI defines cleanup (#14506)

Marlin/src/HAL/HAL_DUE/u8g_com_HAL_DUE_shared_hw_spi.cpp

@@ -66,14 +66,6 @@
 
 #include "../../Marlin.h"
 
-#define SPI_FULL_SPEED      0
-#define SPI_HALF_SPEED      1
-#define SPI_QUARTER_SPEED   2
-#define SPI_EIGHTH_SPEED    3
-#define SPI_SIXTEENTH_SPEED 4
-#define SPI_SPEED_5         5
-#define SPI_SPEED_6         6
-
 void spiBegin();
 void spiInit(uint8_t spiRate);
 void spiSend(uint8_t b);