net/mlx5e: TC, Pass flow attr to attach/detach mod hdr functions

In preparation to remove duplicate functions handling mod hdr allocation
and the fact that modify hdr should be per flow attr and not flow
pass flow attr to the attach and detach mod hdr funcs.

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