refactor types

Just a refactor to make things a bit more compact and
make it easier to talk about uncommon types like
V<float> (FP32 per se) or V<int16_t>.

Change-Id: I9e9873124ef95919dca8f223a2f02c67e1b3560b
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/215943
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed