Remove skcms_EnsureUsableAsDestination*

Change-Id: Iec60fe8109d0f0de743a816f8fa7b295109b8d8e
Reviewed-on: https://skia-review.googlesource.com/125443
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed