mlxsw: spectrum: Set PVID during port initialization

Currently, the driver does not set the port's PVID when initializing a
new port. This is because the driver is using VID 1 as PVID which is the
firmware default.

Subsequent patches are going to change the PVID the driver is setting
when initializing a new port.

Prepare for that by explicitly setting the port's PVID.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>