PPC: Use non prefixed instructions when possible

This CL adds a check to all integer/and fp load/store operations,
if the offset fits in an `is_int16` and if alignment requirements
are met (specific to lwa, ld and std) then a non prefixed load/store
instruction will be used.

Note that operation mode (MRI vs MRR) gets set during instruction selection.

Change-Id: I68e2aa1d559c7ff058d715e6e577a14b590b632b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3669186Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#80765}