split up SkColor_opts_neon.h

Lots of dead code deleted, and the rest moved where it's used.

Change-Id: I9547768592d0dc6c9e9b995c32e21a6e74be7fd1
Reviewed-on: https://skia-review.googlesource.com/c/174313
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
4 files changed