MakeAssemblerBufferExecutable now flushes the i-cache, so we do
not need to do that again.

Change-Id: I46f5619167114cdb84064ef363106bee64282d1f
Reviewed-on: https://chromium-review.googlesource.com/1152813Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#54822}