The register allocator uses std::find to search for an element to be
removed from the active/inactive queues repeatedly. As we already know
the exact position of the element to remove, it is better to use an
iterator right away.

Change-Id: I2cd318a5960113d18b3749b2010f8028fe66158d
Reviewed-on: https://chromium-review.googlesource.com/c/1304542
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57121}