net/mlx5: E-Switch, Normalize the name of uplink vport number

Driver used to name uplink vport as FDB_UPLINK_VPORT, it's hard to
comply with the same naming convention along with the introduction of
other vports. Use MLX5_VPORT as the prefix for such vports and
relocate the uplink vport definition to public header file for the
benefits of both net and IB drivers.

This patch doesn't change any functionality.

Signed-off-by: Bodong Wang <bodong@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>