rt2x00: Fix chipset detection for rt73usb

The lower 4 bytes of the chipset revision must contain
a non-zero value. This bug was introduced by
"rt2x00: Simplify rt2x00_check_rev".

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt73usb.c

@@ -1847,7 +1847,7 @@ static int rt73usb_init_eeprom(struct rt2x00_dev *rt2x00dev)
 	rt2x00_set_chip(rt2x00dev, RT2571, value, reg);
 
 	if (!rt2x00_check_rev(&rt2x00dev->chip, 0x000ffff0, 0x25730) ||
-	    !rt2x00_check_rev(&rt2x00dev->chip, 0x0000000f, 0)) {
+	    rt2x00_check_rev(&rt2x00dev->chip, 0x0000000f, 0)) {
 		ERROR(rt2x00dev, "Invalid RT chipset detected.\n");
 		return -ENODEV;
 	}