rt2x00: Rework alignment check.

Rework the alignment check in rt2x00dev.c to be independent of any
potential alignment measures that may be taken before. Just check
whether the payload is aligned based on the pointer addresses.

Note: This is preparatory for the dynamically mapped skb buffers
for the PCI drivers, as these need 4-byte alignment instead of the
currently enforced offset by 2 bytes.
Signed-off-by: Gertjan van Wingerde <gwingerde@kpnplanet.nl>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -565,13 +565,9 @@ void rt2x00lib_rxdone(struct queue_entry *entry,
 
 	/*
 	 * The data behind the ieee80211 header must be
-	 * aligned on a 4 byte boundary. We already reserved
-	 * 2 bytes for header_size % 4 == 2 optimization.
-	 * To determine the number of bytes which the data
-	 * should be moved to the left, we must add these
-	 * 2 bytes to the header_size.
+	 * aligned on a 4 byte boundary.
 	 */
-	align = (header_size + 2) % 4;
+	align = ((unsigned long)(entry->skb->data + header_size)) & 3;
 
 	if (align) {
 		skb_push(entry->skb, align);