consolidate SkSRGB functions, and remove unused

This kills off the unused routines in this file,
and folds the singly-used routines into sk_linear_to_srgb().

It also takes away the templating.
No one's calling these with anything but Sk4f.

Change-Id: I93ba7c59ea28c9c1a8f852167c31cdb44d53bb5a
Reviewed-on: https://skia-review.googlesource.com/66152
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed