drm/xe/bo: further limit where CCS pages are needed

No need to allocate extra pages for this if we know flat-ccs AUX state
is not even possible, like for normal system memory objects.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>