PSM: Clarify PSM acronym whenever its used in Chromium

PSM abbreviation is not well known when searching for it using
search engine. That is why we need to clarify its acrynom
at least once in each file that its mentioned.

Bug: 1242309
Change-Id: I8b7057650f17ce76a666f834a0ce2556176dad2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3138800


Auto-Submit: Amr Aboelkher <amraboelkher@chromium.org>
Commit-Queue: Amr Aboelkher <amraboelkher@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#917740}