i965: fallback RGBX to RGBA in glEGLImageTargetRenderbufferStorageOES
In the same fashion as is done for glEGLImageTextureTarget2D.
v2: share the fallback which sets baseformat and internalformat correctly
which makes both of the tests pass (Tapani)
Fixes android.hardware.nativehardware.cts.AHardwareBufferNativeTests:
#SingleLayer_ColorTest_GpuColorOutputCpuRead_R8G8B8X8_UNORM
#SingleLayer_ColorTest_GpuColorOutputIsRenderable_R8G8B8X8_UNORM
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>