Remove unfinished ARM F16 compute path

This was a distraction, and there were no plans to finish the
implementation.

Change-Id: I29046c2c4bbf5b402d47112753515416ce8c83cc
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/698183
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed