Use proper SPI timing

include/arm/spi.h

 #define GDO_0 gpioGet(25)
 #define GDO_dir gpioDir(25, DIR_INPUT)
 
-#include "timer.h"
-
-#define NOP() delay_us(1) // could be 62.5ns
+#define NOP() __asm__ __volatile__("nop\n\t" \
+                                   "nop\n\t" \
+                                   "nop\n\t" \
+                                   "nop\n\t" \
+                                   "nop\n\t" \
+                                   "nop\n\t")
 
 #endif