Especially when loading and untagging SMIs within code stubs,
instances of the following pattern appear in the generated code:

    ld    <dst>, <offset>(<base>)
    sradi <dst>,<dst>,32

This CL changes that code to:

    lwa   <dst>, <SmiWordOffset(offset)>(<base>)

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1855533002

Cr-Commit-Position: refs/heads/master@{#35216}