mt76: mt7915: fix possible NULL pointer dereference in mt7915_register_ext_phy

Fix a NULL pointer dereference in mt7915_register_ext_phy since phy
data structure is allocated by mt76_alloc_phy routine
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/init.c

@@ -592,7 +592,6 @@ int mt7915_register_ext_phy(struct mt7915_dev *dev)
 	if (phy)
 		return 0;
 
-	INIT_DELAYED_WORK(&phy->mac_work, mt7915_mac_work);
 	mt7915_cap_dbdc_enable(dev);
 	mphy = mt76_alloc_phy(&dev->mt76, sizeof(*phy), &mt7915_ops);
 	if (!mphy)
@@ -605,6 +604,8 @@ int mt7915_register_ext_phy(struct mt7915_dev *dev)
 	mphy->antenna_mask = BIT(hweight8(phy->chainmask)) - 1;
 	mt7915_init_wiphy(mphy->hw);
 
+	INIT_DELAYED_WORK(&phy->mac_work, mt7915_mac_work);
+
 	/*
 	 * Make the secondary PHY MAC address local without overlapping with
 	 * the usual MAC address allocation scheme on multiple virtual interfaces