mt7601u: null check the allocation

devm_kzalloc may fail and return NULL. So the null check is needed.
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Acked-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt7601u/init.c

@@ -557,6 +557,9 @@ mt76_init_sband_2g(struct mt7601u_dev *dev)
 {
 	dev->sband_2g = devm_kzalloc(dev->dev, sizeof(*dev->sband_2g),
 				     GFP_KERNEL);
+	if (!dev->sband_2g)
+		return -ENOMEM;
+
 	dev->hw->wiphy->bands[NL80211_BAND_2GHZ] = dev->sband_2g;
 
 	WARN_ON(dev->ee->reg.start - 1 + dev->ee->reg.num >