micro_delay in sysutil, used in ti1225, dp8390, fxp and

orinoco now. Uses a combination of tickdelay (where possible) and
calibrated busywait (where necessary).

drivers/fxp/fxp.c

@@ -112,13 +112,9 @@ typedef int irq_hook_t;
 #define structof(type, field, ptr) \
 	((type *) (((char *) (ptr)) - offsetof(type, field)))
 
-#define MICROS_TO_TICKS(m)  (((m)*HZ/1000000)+1)
-
 static timer_t *fxp_timers= NULL;
 static clock_t fxp_next_timeout= 0;
 
-static void micro_delay(unsigned long usecs);
-
 /* ignore interrupt for the moment */
 #define interrupt(x)	0
 
@@ -295,6 +291,9 @@ int main(int argc, char *argv[])
 		fxp_init_buf(fp);
 #endif
 
+	if((r=micro_delay_calibrate()) != OK)
+		panic("FXP","rmicro_delay_calibrate failed", r);
+
 	/* Try to notify inet that we are present (again) */
 	r= ds_retrieve_u32("inet", &tasknr);
 	if (r == OK)
@@ -2875,11 +2874,6 @@ PRIVATE void fxp_expire_timers()
   }
 }
 
-static void micro_delay(unsigned long usecs)
-{
-	tickdelay(MICROS_TO_TICKS(usecs));
-}
-
 static u8_t do_inb(port_t port)
 {
 	int r;