net/mlx5: E-Switch, Check and enable metadata support flag before using

Check E-Switch capabilities and enable metadata support flag
before using it to setup other features that need metadata.

Signed-off-by: Vu Pham <vuhuong@mellanox.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>