common: return uint32_t in CameraBufferMapper::GetNumPlanes

This is to avoid some red herring compile errors in some older toolchains.

BUG=None
TEST=unit tests

Change-Id: I479f391931be2a5d76dcaaec241bb49aca935da1
Reviewed-on: https://chromium-review.googlesource.com/482779
Commit-Ready: Hung-yu Wu <hywu@chromium.org>
Tested-by: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Hung-yu Wu <hywu@chromium.org>
2 files changed