wifi: mt76: mt7921: fix non-PSC channel scan fail

Due to the scan command may only request legacy bands and PSC channel
in 6GHz band, we are unable to scan the APs on non-PSC channel in this
case. Enable WIPHY_FLAG_SPLIT_SCAN_6GHZ to support non-PSC channel
(obtained during scan on legacy bands) in 6GHz scan request.

Fixes: 50ac15a5 ("mt76: mt7921: add 6GHz support")
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7921/init.c

@@ -113,7 +113,8 @@ mt7921_init_wiphy(struct ieee80211_hw *hw)
 	wiphy->max_sched_scan_ssids = MT76_CONNAC_MAX_SCHED_SCAN_SSID;
 	wiphy->max_match_sets = MT76_CONNAC_MAX_SCAN_MATCH;
 	wiphy->max_sched_scan_reqs = 1;
-	wiphy->flags |= WIPHY_FLAG_HAS_CHANNEL_SWITCH;
+	wiphy->flags |= WIPHY_FLAG_HAS_CHANNEL_SWITCH |
+			WIPHY_FLAG_SPLIT_SCAN_6GHZ;
 	wiphy->reg_notifier = mt7921_regd_notifier;
 
 	wiphy->features |= NL80211_FEATURE_SCHED_SCAN_RANDOM_MAC_ADDR |