drm/amdgpu: update the domain flags for dumb buffer creation

After switching to generic framebuffer framework, we rely on the
->dumb_create routine for frame buffer creation. However, the
different domain flags used are not optimal. Add the contiguous
flag to directly allocate the scanout BO as one linear buffer.

Fixes: 087451f3 ("drm/amdgpu: use generic fb helpers instead of setting up AMD own's.")
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

@@ -911,7 +911,8 @@ int amdgpu_mode_dumb_create(struct drm_file *file_priv,
 	struct drm_gem_object *gobj;
 	uint32_t handle;
 	u64 flags = AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED |
-		    AMDGPU_GEM_CREATE_CPU_GTT_USWC;
+		    AMDGPU_GEM_CREATE_CPU_GTT_USWC |
+		    AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS;
 	u32 domain;
 	int r;