drm/amdgpu: Document gfx_off members of struct amdgpu_gfx

Add comments to document gfx_off related members of struct amdgpu_gfx.
Signed-off-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h

@@ -333,11 +333,11 @@ struct amdgpu_gfx {
 
 	/* gfx off */
 	bool                            gfx_off_state;      /* true: enabled, false: disabled */
-	struct mutex                    gfx_off_mutex;
+	struct mutex                    gfx_off_mutex;      /* mutex to change gfxoff state */
 	uint32_t                        gfx_off_req_count;  /* default 1, enable gfx off: dec 1, disable gfx off: add 1 */
-	struct delayed_work             gfx_off_delay_work;
-	uint32_t                        gfx_off_residency;
-	uint64_t                        gfx_off_entrycount;
+	struct delayed_work             gfx_off_delay_work; /* async work to set gfx block off */
+	uint32_t                        gfx_off_residency;  /* last logged residency */
+	uint64_t                        gfx_off_entrycount; /* count of times GPU has get into GFXOFF state */
 
 	/* pipe reservation */
 	struct mutex			pipe_reserve_mutex;