net: dsa: b53: allow leaky reserved multicast

Allow reserved multicast to ignore VLAN membership so STP and other
management protocols work without a PVID VLAN configured when using a
vlan aware bridge.

Fixes: 967dd82 ("net: dsa: b53: Add support for Broadcom RoboSwitch")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250429201710.330937-2-jonas.gorski@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: KanjiMonster

drivers/net/dsa/b53/b53_common.c

@@ -373,9 +373,11 @@ static void b53_enable_vlan(struct b53_device *dev, int port, bool enable,
 		b53_read8(dev, B53_VLAN_PAGE, B53_VLAN_CTRL5, &vc5);
 	}
 
+	vc1 &= ~VC1_RX_MCST_FWD_EN;
+
 	if (enable) {
 		vc0 |= VC0_VLAN_EN | VC0_VID_CHK_EN | VC0_VID_HASH_VID;
-		vc1 |= VC1_RX_MCST_UNTAG_EN | VC1_RX_MCST_FWD_EN;
+		vc1 |= VC1_RX_MCST_UNTAG_EN;
 		vc4 &= ~VC4_ING_VID_CHECK_MASK;
 		if (enable_filtering) {
 			vc4 |= VC4_ING_VID_VIO_DROP << VC4_ING_VID_CHECK_S;
@@ -393,7 +395,7 @@ static void b53_enable_vlan(struct b53_device *dev, int port, bool enable,
 
 	} else {
 		vc0 &= ~(VC0_VLAN_EN | VC0_VID_CHK_EN | VC0_VID_HASH_VID);
-		vc1 &= ~(VC1_RX_MCST_UNTAG_EN | VC1_RX_MCST_FWD_EN);
+		vc1 &= ~VC1_RX_MCST_UNTAG_EN;
 		vc4 &= ~VC4_ING_VID_CHECK_MASK;
 		vc5 &= ~VC5_DROP_VTABLE_MISS;