Fixes a small bug in xxhash. Bug: skia:7647 Change-Id: Ibd0bd8dc4febfe585e257786d9683ea09c94ec6a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2376718Reviewed-by:Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>