Remove SkPM4f

Bug: skia:
Change-Id: If5ed79680f215ac5087469b4c04942885bdb5fd0
Reviewed-on: https://skia-review.googlesource.com/c/159322
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
16 files changed