minigbm: cros_gralloc/buffer: Initialize plane address array

minigbm: cros_gralloc/buffer: Initialize plane address array

Before we return to userspace, we should clear the output array of
pointer values, so that it doesn't contain some spurious data.
Furthermore, if zero flags are given, the lock method itself
dereferences addr[0] before assigning any value there.

BUG=b:38250067
TEST=android.media.cts.DecoderTest on veyron_minnie

Change-Id: I58284477b3813265188f1714f00b1fb7003ed2a3
Reviewed-on: https://chromium-review.googlesource.com/592987
Commit-Ready: Tomasz Figa <tfiga@chromium.org>
Tested-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>