Since we have the ppgtt we want to test, we can ask it directly if it is
suitable for the hugepage test we intend to undertake.

v2: Not everyone has full-ppgtt
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190117230512.4789-1-chris@chris-wilson.co.uk