egl/x11: attribute for dri2_add_config failure
egl/x11: attribute for dri2_add_config failure

... in dri2_x11_add_configs_for_visuals().

Currently the latter does not consider that, thus in such cases it adds
"empty" configs in the list.

Properly account for things and as we do that we can reuse count,
instead of calling _eglGetArraySize to determine if we've added any
configs.

Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>
Reviewed-by: Eric Engestrom <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@engestrom.ch>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler