amdgpu: make AMDGPU_GEM_CREATE_CPU_GTT_USWC flag default

amdgpu: make AMDGPU_GEM_CREATE_CPU_GTT_USWC flag default

amdgpu kernel driver requires USWC flag for allowing bo
allocation in GTT domain, hence enable it by default.

BUG=b:152378755
TEST=On Dali play 4k YouTube video

Signed-off-by: Shirish S <shirish.s@amd.com>
Change-Id: Ic509701f683d184d3fb85b7616dc9a7ed467cfe3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2128147
Tested-by: Bas Nieuwenhuizen <basni@chromium.org>
Reviewed-by: Bas Nieuwenhuizen <basni@chromium.org>
Reviewed-by: Drew Davenport <ddavenport@chromium.org>