net/mlx5: E-Switch, Remove redundant check

The call to mlx5_eswitch_enable() also does the same check
and if E-Switch not supported it returns 0 without any change.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>