goldfish-opengl: nuke PixelFormat

HAL formats are more widely used and available in Android compat
layers.  5551 and 4444 removed earlier:

https://android.googlesource.com/platform/frameworks/native/+/c2414bb%5E%21/

BUG=202552093
TEST=compile

Change-Id: Ic553c6bca2bb1e24b24ad576943686b5d0ff4fa5
2 files changed