[sparkplug] Re-fix frame fill on arm64

We had an off-by-one in the arm64 frame fill code due to double counting
the register already pushed by the prologue.

Bug: v8:11420
Change-Id: I9b4a3bcdc913886f0ba7a316f23f41eed3fc9311
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2707168


Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72872}