sfc: MAE functions to create/update/delete encap headers

Besides the raw header data, also pass the tunnel type, so that the
 hardware knows it needs to update the IP Total Length and UDP Length
 fields (and corresponding checksums) for each packet.
Also, populate the ENCAP_HEADER_ID field in efx_mae_alloc_action_set()
 with the fw_id returned from efx_mae_allocate_encap_md().

Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>