In this CL we fix the emitted code for Load Splat and Load Extend.
Load Splat loads a byte, half word, word or double word based
on the specific opcode.

Load Extend always loads a double word and then unpacks it
accordingly.

Change-Id: Ic1619c81a58f4997d69612f08edb6975d17e8bb3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2568132Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#71543}