The size of flag is now 16 bits.

Bug: v8:12161
Change-Id: I5db5e05171281f27cce739c7b76e1d4b9ebf20b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3602236Reviewed-by: Jakob Linke <jgruber@chromium.org>
Commit-Queue: Yu Liu <liuyu@loongson.cn>
Cr-Commit-Position: refs/heads/main@{#80165}