Disable test on big endian PPC for now, since it
is missing load/store reverse byte instructions.

R=machenbach@chromium.org, jkummerow@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com
BUG=
LOG=N

Change-Id: Iaf12a14678bc9d113dc4d11998ea5bad158c20fd
Reviewed-on: https://chromium-review.googlesource.com/634271Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#47587}