Even though a previous patch made the number of slots pushed/claimed on
the stack aligned, the boundary between frames was not a multiple of
two slots as well. We were pushing the number of arguments (which belongs
in the ArgumentAdaptor frame) together with the arguments to pass to the
callee (which belong to the frame of the callee). Those need to be
separated so we can drop the arguments without messing up the alignment.

Bug: v8:6644
Change-Id: I259c58db33a7c2726e5a3c74bcd67496f607d1d0
Reviewed-on: https://chromium-review.googlesource.com/793047Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#49759}