Turn cases where we are multiplying with a power of two into a left shift. We
hit this optimisation roughly 500 times in the snapshot.

Bug: 
Change-Id: Ibd3104a3dbe49f247a2d84db94891f6e3a897026
Reviewed-on: https://chromium-review.googlesource.com/763229Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/master@{#49306}