drm/xe/huc: HuC authentication via GSC

HuC authentication via GSC is performed by submitting the appropriate
PXP packet to the GSC FW. This packet can trigger a "pending" reply from
the FW, so we need to handle that and resubmit. Note that the auth via
GSC can only be performed if the HuC has already been authenticated by
the GuC.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Vivaik Balasubrawmanian <vivaik.balasubrawmanian@intel.com>
Reviewed-by: Vivaik Balasubrawmanian <vivaik.balasubrawmanian@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>