mt76: fix returnvar.cocci warnings

drivers/net/wireless/mediatek/mt76/mt76x2_main.c:86:5-8: Unneeded variable: "ret". Return "0" on line 112

 Remove unneeded variable used to store return value.

Generated by: scripts/coccinelle/misc/returnvar.cocci

Fixes: a5f6039c8f9c ("mt76: add driver code for MT76x2e")
CC: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt76/mt76x2_main.c

@@ -83,7 +83,6 @@ mt76x2_add_interface(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
 	struct mt76x2_dev *dev = hw->priv;
 	struct mt76x2_vif *mvif = (struct mt76x2_vif *) vif->drv_priv;
 	unsigned int idx = 0;
-	int ret = 0;
 
 	if (vif->addr[0] & BIT(1))
 		idx = 1 + (((dev->mt76.macaddr[0] ^ vif->addr[0]) >> 2) & 7);
@@ -109,7 +108,7 @@ mt76x2_add_interface(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
 	mvif->group_wcid.hw_key_idx = -1;
 	mt76x2_txq_init(dev, vif->txq);
 
-	return ret;
+	return 0;
 }
 
 static void