drm/amdkfd: apply uncached flag for aldebaran

The flag is only applied on fine-grained memory.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Oak Zeng <Oak.Zeng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>