wifi: mt76: mt7996: let upper layer handle MGMT frame protection

The firmware support for management frame protection has limitations:
- do not support cipher BIP-GMAC-128 and BIP-GMAC-256
- support cipher BIP-CMAC-128 and BIP-CMAC-256, except action frame with
  action type 'not robust'.

Therefore, to simplify the logic, do not set the IGTK to firmware and
let the encryption of management frames be handled by upper layer.
Signed-off-by: Michael-CY Lee <michael-cy.lee@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7996/main.c

@@ -352,10 +352,6 @@ static int mt7996_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 
 	/* fall back to sw encryption for unsupported ciphers */
 	switch (key->cipher) {
-	case WLAN_CIPHER_SUITE_AES_CMAC:
-		wcid_keyidx = &wcid->hw_key_idx2;
-		key->flags |= IEEE80211_KEY_FLAG_GENERATE_MMIE;
-		break;
 	case WLAN_CIPHER_SUITE_TKIP:
 	case WLAN_CIPHER_SUITE_CCMP:
 	case WLAN_CIPHER_SUITE_CCMP_256:
@@ -363,6 +359,11 @@ static int mt7996_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 	case WLAN_CIPHER_SUITE_GCMP_256:
 	case WLAN_CIPHER_SUITE_SMS4:
 		break;
+	case WLAN_CIPHER_SUITE_AES_CMAC:
+		wcid_keyidx = &wcid->hw_key_idx2;
+		key->flags |= IEEE80211_KEY_FLAG_GENERATE_MMIE;
+		fallthrough;
+	case WLAN_CIPHER_SUITE_BIP_CMAC_256:
 	case WLAN_CIPHER_SUITE_BIP_GMAC_128:
 	case WLAN_CIPHER_SUITE_BIP_GMAC_256:
 		if (key->keyidx == 6 || key->keyidx == 7)