This changes the interface descriptor for the frame dropper trampoline
to not use the kRootRegister (ebx) anymore.

Change-Id: I15df6af57f70d8aeea6c97298b437ad96af19cd4
Bug: v8:6666
Reviewed-on: https://chromium-review.googlesource.com/1193242
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55484}