drm/amdgpu: implement PRT for GFX6 v2

Enable/disable the handling globally for now and
print a warning when we enable it for the first time.

v2: write to the correct register, adjust bits to that hw generation
v3: fix compilation, add the missing register bit definitions

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index b921253..3edc871 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -569,6 +569,7 @@ struct amdgpu_mc {
 	uint32_t		vram_type;
 	uint32_t                srbm_soft_reset;
 	struct amdgpu_mode_mc_save save;
+	bool			prt_warning;
 };
 
 /*