mlxsw: reg: Add Switch Port VLAN MAC Learning register definition

Since we currently do not support the offloading of 802.1D bridges, we
need to be able to let the device know it should not learn MAC addresses
on specific {Port, VID} pairs.

Add the SPVMLR register, which controls the learning enablement of
{Port, VID} pairs.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>