kernel: Backport mv88e6xxx patch to keep pvid at 0 if VLAN-unaware and remove hack

Keeping the pvid at 0 when VLAN-unaware makes it possible to drop the
hack introduced in commit 920eaab1d8 ("kernel: DSA roaming fix for
Marvell mv88e6xxx"). Dropping the hack makes it possible to use VLAN
interfaces with VID 1 on DSA ports without problems with FDB.

Signed-off-by: Marek Behún <kabel@kernel.org>
(cherry picked from commit 9caa6f0aa7)
Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
[drop kernel patch hack from Linux version 5.15, drop paragraph about
backport patch, which is not necessary as it is included in kernel 5.15]

target/linux/generic/hack-5.15/710-net-dsa-mv88e6xxx-default-VID-1.patch

@@ -1,18 +0,0 @@
---- a/drivers/net/dsa/mv88e6xxx/chip.c
-+++ b/drivers/net/dsa/mv88e6xxx/chip.c
-@@ -2321,6 +2321,7 @@ static int mv88e6xxx_port_fdb_add(struct
- 	struct mv88e6xxx_chip *chip = ds->priv;
- 	int err;
- 
-+	vid = vid ? : 1;
- 	mv88e6xxx_reg_lock(chip);
- 	err = mv88e6xxx_port_db_load_purge(chip, port, addr, vid,
- 					   MV88E6XXX_G1_ATU_DATA_STATE_UC_STATIC);
-@@ -2335,6 +2336,7 @@ static int mv88e6xxx_port_fdb_del(struct
- 	struct mv88e6xxx_chip *chip = ds->priv;
- 	int err;
- 
-+	vid = vid ? : 1;
- 	mv88e6xxx_reg_lock(chip);
- 	err = mv88e6xxx_port_db_load_purge(chip, port, addr, vid, 0);
- 	mv88e6xxx_reg_unlock(chip);