net: dsa: bcm_sf2: Fix Wake-on-LAN with mac_link_down()

[ Upstream commit b7be130 ]

After commit 2d1f90f ("net: dsa/bcm_sf2: fix incorrect usage of
state->link") the interface suspend path would call our mac_link_down()
call back which would forcibly set the link down, thus preventing
Wake-on-LAN packets from reaching our management port.

Fix this by looking at whether the port is enabled for Wake-on-LAN and
not clearing the link status in that case to let packets go through.

Fixes: 2d1f90f ("net: dsa/bcm_sf2: fix incorrect usage of state->link")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220512021731.2494261-1-f.fainelli@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/dsa/bcm_sf2.c

@@ -710,6 +710,9 @@ static void bcm_sf2_sw_mac_link_down(struct dsa_switch *ds, int port,
 	struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
 	u32 reg, offset;
 
+	if (priv->wol_ports_mask & BIT(port))
+		return;
+
 	if (port != core_readl(priv, CORE_IMP0_PRT_ID)) {
 		if (priv->type == BCM7445_DEVICE_ID)
 			offset = CORE_STS_OVERRIDE_GMIIP_PORT(port);