Updated the head status flag in the head control register.

src/head_tracking.c

@@ -69,11 +69,13 @@ uint16_t head_tracking_get_period(void)
 void head_tracking_start(void)
 {
   head_tracking_enabled=0x01;
+  ram_data[DARWIN_HEAD_CNTRL]|=HEAD_STATUS;
 }
 
 void head_tracking_stop(void)
 {
   head_tracking_enabled=0x00;
+  ram_data[DARWIN_HEAD_CNTRL]&=(~HEAD_STATUS);
 }
 
 uint8_t head_is_tracking(void)