zd1211rw: Fix multicast filtering.

If multicast parameter (as returned by zd_op_prepare_multicast) has
changed, no bit in changed_flags is set. To handle this situation, we do
not return if changed_flags is 0. If we do so, we will have some issue
with IPv6 which uses multicast for link layer address resolution.
Signed-off-by: NBenoit Papillault <benoit.papillault@free.fr>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/zd1211rw/zd_mac.c

@@ -987,12 +987,13 @@ static void zd_op_configure_filter(struct ieee80211_hw *hw,
 	changed_flags &= SUPPORTED_FIF_FLAGS;
 	*new_flags &= SUPPORTED_FIF_FLAGS;
 
-	/* changed_flags is always populated but this driver
-	 * doesn't support all FIF flags so its possible we don't
-	 * need to do anything */
-	if (!changed_flags)
-		return;
-
+	/*
+	 * If multicast parameter (as returned by zd_op_prepare_multicast)
+	 * has changed, no bit in changed_flags is set. To handle this
+	 * situation, we do not return if changed_flags is 0. If we do so,
+	 * we will have some issue with IPv6 which uses multicast for link
+	 * layer address resolution.
+	 */
 	if (*new_flags & (FIF_PROMISC_IN_BSS | FIF_ALLMULTI))
 		zd_mc_add_all(&hash);