Hide GrBackendTexture/RenderTarget constructors that take a GrPixelConfig

Make GrGLTexture use the version that takes GrMipMapped.

Bug: skia:6718
Change-Id: Id3e801bcb5e781938e610bdea75bd92498117935
Reviewed-on: https://skia-review.googlesource.com/116221
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
3 files changed