net/mlx5e: TC, refactor access to hash key

Currently, a temp object is filled and used as a key for rhashtable_lookup.
Lookups will only works while key remains the first attribute in the
relevant rhashtable node object.

Fix this by passing a key, instead of a object containing the key.

Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>