airo: Fix integer overflow warning

On BigEndian gcc complains:

drivers/net/wireless/airo.c: In function ‘sniffing_mode’:
drivers/net/wireless/airo.c:4809: warning: integer overflow in expression

Fix this by doing the bitwise AND on the host-endian value.
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/airo.c

@@ -4806,7 +4806,7 @@ static int airo_config_commit(struct net_device *dev,
 
 static inline int sniffing_mode(struct airo_info *ai)
 {
-	return le16_to_cpu(ai->config.rmode & RXMODE_MASK) >=
+	return (le16_to_cpu(ai->config.rmode) & le16_to_cpu(RXMODE_MASK)) >=
 		le16_to_cpu(RXMODE_RFMON);
 }