Including `weston-egl-ext.h` causes compilation failure for configurations
with EGL disabled.
Verified with `--disable-egl`, `--disable-x11-compositor`
and `--disable-drm-compositor`.
Signed-off-by: Krzysztof Konopko <kris@youview.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>