net/mlx5: Fix required capability for manipulating MPFS

Manipulating of the MPFS requires eswitch manager capabilities.

Fixes: eeb66cdb

 ('net/mlx5: Separate between E-Switch and MPFS')
Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>