Remove SkPM4f.h, fold contents into SkColorData.h

Bug: skia:
Change-Id: I942e46c2b680714cdd10f7393c6a4d206df645a8
Reviewed-on: https://skia-review.googlesource.com/c/167394
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
22 files changed