zephyrCommon: Implement micros() and millis()

Call Zephyr kernel timing functions from Arduino timing api

Signed-off-by: Mike Szczys <mike@golioth.io>

Author: szczys

cores/arduino/zephyrCommon.cpp

@@ -37,4 +37,11 @@ PinStatus digitalRead(pin_size_t pinNumber) {
 
 void delay(unsigned long ms) { k_sleep(K_MSEC(ms)); }
 
-void delayMicroseconds(unsigned int us) { k_sleep(K_USEC(us)); }
+void delayMicroseconds(unsigned int us) { k_sleep(K_USEC(us)); }
+
+unsigned long micros(void) {
+  return k_cyc_to_us_floor32(k_cycle_get_32());
+}
+
+unsigned long millis(void) { return k_uptime_get_32(); }
+