drm/i915/ppgtt: Break loop in gen8_ppgtt_clear_range failure path
drm/i915/ppgtt: Break loop in gen8_ppgtt_clear_range failure path

If for some reason [1], the page directory/table does not exist, clear_range
would end up in an infinite while loop.

Introduced by commit 06fda602dbca ("drm/i915: Create page table allocators").

[1] This is already being addressed in one of Mika's patches:
http://mid.gmane.org/1432314314-23530-17-git-send-email-cd221c71e765d1ce593d15b204fee351fb09fd98@intel.com

Cc: Mika Kuoppala <cd221c71e765d1ce593d15b204fee351fb09fd98@linux.intel.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org
Reported-by: John Harrison <cad4767e5b1a5b87d969025bd160bf28dab2f11e@intel.com>
Signed-off-by: Michel Thierry <c65ff7d3dfaea3345301797f027f123ededb124c@intel.com>
Reviewed-by: Mika Kuoppala <cd221c71e765d1ce593d15b204fee351fb09fd98@intel.com>
Signed-off-by: Jani Nikula <ba783f3beccaedfda693f41a15407d612a629408@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs