net: lan966x: Fix usage of lan966x->mac_lock when entry is added

To add an entry to the MAC table, it is required first to setup the
entry and then issue a command for the MAC to learn the entry.
So if it happens for two threads to add simultaneously an entry in MAC
table then it would be a race condition.
Fix this by using lan966x->mac_lock to protect the HW access.

Fixes: fc0c3fe7 ("net: lan966x: Add function lan966x_mac_ip_learn()")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/lan966x/lan966x_mac.c

@@ -75,6 +75,9 @@ static int __lan966x_mac_learn(struct lan966x *lan966x, int pgid,
 			       unsigned int vid,
 			       enum macaccess_entry_type type)
 {
+	int ret;
+
+	spin_lock(&lan966x->mac_lock);
 	lan966x_mac_select(lan966x, mac, vid);
 
 	/* Issue a write command */
@@ -86,7 +89,10 @@ static int __lan966x_mac_learn(struct lan966x *lan966x, int pgid,
 	       ANA_MACACCESS_MAC_TABLE_CMD_SET(MACACCESS_CMD_LEARN),
 	       lan966x, ANA_MACACCESS);
 
-	return lan966x_mac_wait_for_completion(lan966x);
+	ret = lan966x_mac_wait_for_completion(lan966x);
+	spin_unlock(&lan966x->mac_lock);
+
+	return ret;
 }
 
 /* The mask of the front ports is encoded inside the mac parameter via a call