rt2800: replace mdelay by usleep on vco calibration.

This procedure can sleep, hence mdelay is not needed.
Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

@@ -4352,7 +4352,7 @@ void rt2800_vco_calibration(struct rt2x00_dev *rt2x00dev)
 		return;
 	}
 
-	mdelay(1);
+	usleep_range(1000, 1500);
 
 	rt2800_register_read(rt2x00dev, TX_PIN_CFG, &tx_pin);
 	if (rt2x00dev->rf_channel <= 14) {