Merge pull request #308 from FrankBoesing/patch-2

optimized delayNanoseconds

teensy4/core_pins.h

 static inline void delayNanoseconds(uint32_t nsec)
 {
 	uint32_t begin = ARM_DWT_CYCCNT;
-	uint32_t cycles =  ((uint64_t)F_CPU_ACTUAL * nsec) / 1000000000UL;
+	uint32_t cycles =   ((F_CPU_ACTUAL>>16) * nsec) / (1000000000UL>>16);
 	while (ARM_DWT_CYCCNT - begin < cycles) ; // wait
 }