drm/i915/huc: Support HuC authentication

The HuC authentication is done by host2guc call. The HuC RSA keys
are sent to GuC for authentication.

v2: rebased on top of drm-tip. Changed name format and upped
version 1.7.
v3: changed wait_for_atomic to wait_for
v4: rebased. Rename intel_huc_auh() to intel_guc_auth_huc()
and place the prototype in intel_guc.h,correct the comments.
v5: rebased. Moved intel_guc_auth_huc from i915_guc_submission.c
to intel_uc.c.Update dev to dev_priv in intel_guc_auth_huc().
Renamed HOST2GUC_ACTION_AUTHENTICATE_HUC TO INTEL_GUC_ACTION_
AUTHENTICATE_HUC
v6: rebased. Add newline on DRM_ERRORs that already dont have one.
v7: rebased. Replace wait_for with intel_wait_for_register() since
the latter employs sleep optimisations for quick responses- as pointed
out by Chris Wilson.
v8: rebased. Cleanup the intel_guc_auth_huc() by removing checks
already performed in earlier functions. Make comments more descriptive.
v9: rebased. Changed the bias for pinning the HuC object. Move
intel_guc_auth_huc() to intel_huc.c. Change DRM_DEBUGs to DRM_ERRORs
in intel_guc_auth_huc(). Add return status to DRM_ERRORs.
v10: Remove message not required for the user..

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Tested-by: Xiang Haihao <haihao.xiang@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Alex Dai <yu.dai@intel.com>
Signed-off-by: Peter Antoine <peter.antoine@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1484755558-1234-5-git-send-email-anusha.srivatsa@intel.com