drm/amdgpu: cleanup initializing gtt_size

Stop spreading the code over all GMC generations.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@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 20e0ed9..df63823 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -559,6 +559,7 @@ struct amdgpu_gart {
 	const struct amdgpu_gart_funcs *gart_funcs;
 };
 
+void amdgpu_gart_set_defaults(struct amdgpu_device *adev);
 int amdgpu_gart_table_ram_alloc(struct amdgpu_device *adev);
 void amdgpu_gart_table_ram_free(struct amdgpu_device *adev);
 int amdgpu_gart_table_vram_alloc(struct amdgpu_device *adev);