net: dsa: vsc73xx: implement FDB operations

This commit introduces implementations of three functions:
.port_fdb_dump
.port_fdb_add
.port_fdb_del

The FDB database organization is the same as in other old Vitesse chips:
It has 2048 rows and 4 columns (buckets). The row index is calculated by
the hash function 'vsc73xx_calc_hash' and the FDB entry must be placed
exactly into row[hash]. The chip selects the bucket number by itself.
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Link: https://patch.msgid.link/20240827123938.582789-1-paweldembicki@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/dsa/vitesse-vsc73xx.h

@@ -45,6 +45,7 @@ struct vsc73xx_portinfo {
  * @vlans: List of configured vlans. Contains port mask and untagged status of
  *	every vlan configured in port vlan operation. It doesn't cover tag_8021q
  *	vlans.
+ * @fdb_lock: Mutex protects fdb access
  */
 struct vsc73xx {
 	struct device			*dev;
@@ -57,6 +58,7 @@ struct vsc73xx {
 	void				*priv;
 	struct vsc73xx_portinfo		portinfo[VSC73XX_MAX_NUM_PORTS];
 	struct list_head		vlans;
+	struct mutex			fdb_lock;
 };
 
 /**