egl: Emit correct error when robust context creation fails

egl: Emit correct error when robust context creation fails

Fixes dEQP-EGL.functional.create_context_ext.robust_*
on Intel with GBM.

If the user sets the EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR in
EGL_CONTEXT_FLAGS_KHR when creating an OpenGL ES context, then
EGL_KHR_create_context spec requires that we unconditionally emit
EGL_BAD_ATTRIBUTE because that flag does not exist for OpenGL ES. When
creating an OpenGL context, the spec requires that we emit EGL_BAD_MATCH
if we can't support the request; that error is generated in the egl_dri2
layer where the driver capability is actually checked.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99188
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>