egl/gbm: Ensure EGLConfigs match GBM surface format

egl/gbm: Ensure EGLConfigs match GBM surface format

When we create an EGL window surface on a GBM surface, ensure that the
EGLConfig is compatible with the GBM format, notwithstanding XRGB/ARGB
interchange.

For example, rendering with an XRGB8888 EGLConfig on to an ARGB8888
gbm_surface (and vice-versa) are acceptable, but rendering with an
XRGB2101010 EGLConfig on to an XRGB8888 gbm_surface will now be
rejected.

This was previously allowed through; when 10bpc formats were enabled,
clients which picked a completely random EGL config and hoped/assumed
they were XRGB8888 would break.

If you have bisected a failure to start a GBM/KMS client to this commit,
please look at its EGLConfig selection (e.g. through eglChooseConfigs),
and add an EGL_NATIVE_VISUAL_ID == gbm_surface format match to the
attribs for config selection.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Tested-by: Ilia Mirkin <imirkin@alum.mit.edu>