drm/i915/doc: Include GuC ABI documentation

GuC ABI documentation is now ready to be included in i915.rst
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210616001302.84233-4-matthew.brost@intel.com

Documentation/gpu/i915.rst

@@ -523,6 +523,14 @@ GuC-based command submission
 .. kernel-doc:: drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
    :doc: GuC-based command submission
 
+GuC ABI
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: drivers/gpu/drm/i915/gt/uc/abi/guc_messages_abi.h
+.. kernel-doc:: drivers/gpu/drm/i915/gt/uc/abi/guc_communication_mmio_abi.h
+.. kernel-doc:: drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h
+.. kernel-doc:: drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
+
 HuC
 ---
 .. kernel-doc:: drivers/gpu/drm/i915/gt/uc/intel_huc.c