When PVID is removed from a bridge port, the Linux bridge drops both
untagged and prio-tagged packets. Align mlxsw with this behavior.

Fixes: 148f472d ("mlxsw: reg: Add the Switch Port Acceptable Frame Types register")
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>