Metal:remove TextureMtl::mIsPow2 Bug: angleproject:7147 Change-Id: I60876d719989311de07ad97f1be5daecb83c3801 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3564276 Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Kyle Piddington <kpiddington@apple.com> Commit-Queue: Gregg Tavares <gman@chromium.org>