add x-macro over SkVM::Ops

This streamlines the dump() methods a bit,
and makes it easier to see what ops have not
yet been implemented in the JIT.

Change-Id: I22d0a206e847451452be75b586c8b15eb0c1af78
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263456
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed