at86rf230: change reset timings

While checkpatch another patch I got a:

"WARNING: msleep < 20ms can sleep for up to 20ms"

The datasheet of at86rf231 and at86rf212 says a minimum delay for reset
pulse width and spi access latency after reset is 625 nanoseconds.

This patch removes the 1 milliseconds sleep and replace it with a 1
microseconds udelay which should be also okay for the reset pulse width.

To change the state from RESET -> TRX_OFF the at86rf230 device needs 120
microseconds, this is a worst case of all at86rf* chips.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ieee802154/at86rf230.c

@@ -1080,11 +1080,11 @@ static int at86rf230_probe(struct spi_device *spi)
 	}
 
 	/* Reset */
-	msleep(1);
+	udelay(1);
 	gpio_set_value(pdata->rstn, 0);
-	msleep(1);
+	udelay(1);
 	gpio_set_value(pdata->rstn, 1);
-	msleep(1);
+	usleep_range(120, 240);
 
 	rc = __at86rf230_detect_device(spi, &man_id, &part, &version);
 	if (rc < 0)