Remove private configs from GrPixelConfig.

GrPixelConfig is no longer public so there is no need for us to have the
special private configs.

Bug: skia:
Change-Id: Id732a3b2db3a7b9fd5d767e5548e796a4e670547
Reviewed-on: https://skia-review.googlesource.com/c/191572
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed