Add AVX-512 detection to SkCpu

I've added a SKY alias for the five new bits detected on a Skylake Xeon.

Change-Id: I9f7dd48f4dc866608d81befd061434ca325ef451
Reviewed-on: https://skia-review.googlesource.com/9043
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
2 files changed