qtnfmac: remove duplicated assignment to mac

mac is being assigned twice, remove redundant 2nd assignment.

Detected by CoverityScan, CID#1437554 ("Incorrect expression")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/quantenna/qtnfmac/cfg80211.c

@@ -922,7 +922,7 @@ void qtnf_netdev_updown(struct net_device *ndev, bool up)
 void qtnf_virtual_intf_cleanup(struct net_device *ndev)
 {
 	struct qtnf_vif *vif = qtnf_netdev_get_priv(ndev);
-	struct qtnf_wmac *mac = mac = wiphy_priv(vif->wdev.wiphy);
+	struct qtnf_wmac *mac = wiphy_priv(vif->wdev.wiphy);
 
 	if (vif->wdev.iftype == NL80211_IFTYPE_STATION) {
 		switch (vif->sta_state) {