net/mlx5: Remove redundant esw multiport validate function

The function didn't validate the value and doesn't require value
validation as it will always be valid true or false values.

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