net/mlx5e: Rename some encap-specific API to generic names

Some of the encap-specific functions and fields will also be used by route
update infrastructure in following patches. Rename them to generic names.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>