ppc: [liftoff] more conversion from float to int

Change-Id: Ie3778dfc1b477a234399d58dd78ef1a3c1195b4d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3166250


Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76888}