drm/i915: Timeout lowlevel_hole GTT selftest early

Check for a timeout in the lowlevel_hole GTT before we allocate state
for that pass, as our cleanup phase stops on the iteration before the
timeout.

References: https://bugs.freedesktop.org/show_bug.cgi?id=99947


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170224193315.21072-1-chris@chris-wilson.co.uk


Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>