net/mlx5e: Add post meter table for flow metering

Flow meter object monitors the packets rate for the flows it is
attached to, and color packets with GREEN or RED. The post meter table
is used to check the color. Packet is dropped if it's RED, or
forwarded to post_act table if GREEN.

Packet color will be set to 8 LSB of the register C5, so they are
reserved for metering, which are previously used for matching fte id.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Ariel Levkovich <lariel@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>