IB/mlx5: Disable self loopback check when in switchdev mode

When in switchdev mode, there is no need to do self loopback checks
as we can't receive those packets, we insert steering rules to the
eswitch that make sure packets can't be looped back.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>