Due compatibility

Trivial changes for Due compatibility

Adafruit_RA8875.cpp

@@ -72,8 +72,10 @@ boolean Adafruit_RA8875::begin(enum RA8875sizes s) {
   delay(100);
   
   SPI.begin();
+#ifdef __AVR__
   SPI.setClockDivider(SPI_CLOCK_DIV128);
   SPI.setDataMode(SPI_MODE0);
+#endif
   
   if (readReg(0) != 0x75) {
     return false;
@@ -81,8 +83,9 @@ boolean Adafruit_RA8875::begin(enum RA8875sizes s) {
 
   initialize();
 
+#ifdef __AVR__
   SPI.setClockDivider(SPI_CLOCK_DIV4);
-
+#endif
   return true;
 }
 

Adafruit_RA8875.h

@@ -50,7 +50,7 @@ typedef struct Point
   int32_t y;
 } tsPoint_t;
 
-typedef struct Matrix 
+typedef struct //Matrix
 {
   int32_t An,
           Bn,