Remove DSL swizzle support.

This is now dead code.

Change-Id: I69dbdcc7adf883aae975e8a2276169fb91f49346
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/696176
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
6 files changed