mt76: mt7615: improve wmm index allocation

Typically all AP interfaces on a PHY will share the same WMM settings, while
sta/mesh interfaces will usually inherit the settings from a remote device.
In order minimize the likelihood of conflicting WMM settings, make all AP
interfaces share one slot, and all non-AP interfaces another one.

This also fixes running multiple AP interfaces on MT7613, which only has 3
WMM slots.
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/main.c

@@ -208,11 +208,9 @@ static int mt7615_add_interface(struct ieee80211_hw *hw,
 	mvif->mt76.omac_idx = idx;
 
 	mvif->mt76.band_idx = ext_phy;
-	if (mt7615_ext_phy(dev))
-		mvif->mt76.wmm_idx = ext_phy * (MT7615_MAX_WMM_SETS / 2) +
-				mvif->mt76.idx % (MT7615_MAX_WMM_SETS / 2);
-	else
-		mvif->mt76.wmm_idx = mvif->mt76.idx % MT7615_MAX_WMM_SETS;
+	mvif->mt76.wmm_idx = vif->type != NL80211_IFTYPE_AP;
+	if (ext_phy)
+		mvif->mt76.wmm_idx += 2;
 
 	dev->mt76.vif_mask |= BIT(mvif->mt76.idx);
 	dev->omac_mask |= BIT_ULL(mvif->mt76.omac_idx);