drivers/net/wireless/rt2x00/rt2x00dev.c: remove null test before kfree

Fix checkpatch warning:
WARNING: kfree(NULL) is safe this check is probably not required

Cc: Ivo van Doorn <IvDoorn@gmail.com>
Cc: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -1455,8 +1455,7 @@ void rt2x00lib_remove_dev(struct rt2x00_dev *rt2x00dev)
 	/*
 	 * Free the driver data.
 	 */
-	if (rt2x00dev->drv_data)
-		kfree(rt2x00dev->drv_data);
+	kfree(rt2x00dev->drv_data);
 }
 EXPORT_SYMBOL_GPL(rt2x00lib_remove_dev);