drm/amdgpu: add basic PRT support (v2)

Future hardware generations can handle PRT flags on a per page basis,
but current hardware can only turn it on globally.

Add the basic handling for both, a global callback to enable/disable
triggered by setting a per mapping flag.

v2: agd: rebase fixes

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 c1b9135..618f128 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -294,6 +294,8 @@ struct amdgpu_gart_funcs {
 			   uint32_t gpu_page_idx, /* pte/pde to update */
 			   uint64_t addr, /* addr to write into pte/pde */
 			   uint32_t flags); /* access flags */
+	/* enable/disable PRT support */
+	void (*set_prt)(struct amdgpu_device *adev, bool enable);
 };
 
 /* provided by the ih block */