mac80211: fix "‘ret’ may be used uninitialized" warning

net/mac80211/ht.c: In function ‘ieee80211_start_tx_ba_session’:
net/mac80211/ht.c:472: warning: ‘ret’ may be used uninitialized in this function
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/ht.c

@@ -469,7 +469,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 	struct ieee80211_sub_if_data *sdata;
 	u16 start_seq_num;
 	u8 *state;
-	int ret;
+	int ret = 0;
 
 	if ((tid >= STA_TID_NUM) || !(hw->flags & IEEE80211_HW_AMPDU_AGGREGATION))
 		return -EINVAL;