rt2800: add disabling of DMA before loading firmware

Legacy driver disables DMA before loading firmware.
Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Reviewed-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -426,6 +426,8 @@ int rt2800_load_firmware(struct rt2x00_dev *rt2x00dev,
 		rt2800_register_write(rt2x00dev, PWR_PIN_CFG, 0x00000002);
 	}
 
+	rt2800_disable_wpdma(rt2x00dev);
+
 	/*
 	 * Write firmware to the device.
 	 */