movsx_b needs a byte register on ia32, but is using arbitrary gp register.

Bug: v8:9909
Change-Id: I5f31733ccf4ca3b04a3564a9133aec496653079e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2158928Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Fanchen Kong <fanchen.kong@intel.com>
Cr-Commit-Position: refs/heads/master@{#67351}