net/mlx5e: Allow to match on MPLS parameters only for MPLS over UDP

Currently, we support hardware offload only for MPLS over UDP.
However, rules matching on MPLS parameters are now wrongly offloaded
for regular MPLS, without actually taking the parameters into
consideration when doing the offload.
Fix it by rejecting such unsupported rules.

Fixes: 72046a91

 ("net/mlx5e: Allow to match on mpls parameters")
Signed-off-by: Alaa Hleihel <alaa@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>