ppc: [liftoff] implement conversion from float to int

Change-Id: I56592c8abf48c30ecdc1f4ce3084bd373a5930d9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3165691


Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76886}