opengles emulator: filter-out non-RGB configs

some applications and conformance tests expects to have
non-zero bit counts for all red,green and blue channels.
The translator expose all EGL compliant configs, including
monochrome and RG configs.
We now filter those out and expose to the guest only the RGB
configs.

Change-Id: I9a293675359135a548ce1c089f31a48ea2b7f46e
1 file changed