which: upgraded package to upstream

Upgraded sys-apps/which to version 2.21 on amd64, arm, x86

TEST=Ran which -v, which which and verified results on grunt, kevin and
santa boards.

Change-Id: I865f7fbf1e67b7050e8d35463ad7fb94ba993387
Reviewed-on: https://chromium-review.googlesource.com/1216844
Commit-Ready: Paul Moy <pmoy@chromium.org>
Tested-by: Paul Moy <pmoy@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
5 files changed