staging: rtl8192u: fix incorrect type in assignment in ieee80211_tx.c

This patch fixes the following sparse warning:
ieee80211_tx.c:174:36: incorrect type in assignment (different base types)
ieee80211_tx.c:174:36: expected unsigned short [unsigned] [short] [usertype] <noident>
ieee80211_tx.c:174:36: got restricted __be16 [usertype] <noident>

by adding left side cast to __be16.
Signed-off-by: Martin Karamihov <martinowar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_tx.c

@@ -171,7 +171,7 @@ static inline int ieee80211_put_snap(u8 *data, u16 h_proto)
 	snap->oui[1] = oui[1];
 	snap->oui[2] = oui[2];
 
-	*(u16 *)(data + SNAP_SIZE) = htons(h_proto);
+	*(__be16 *)(data + SNAP_SIZE) = htons(h_proto);
 
 	return SNAP_SIZE + sizeof(u16);
 }