egl: error out on eglCreateWaylandBufferFromImageWL

egl: error out on eglCreateWaylandBufferFromImageWL

Currently f one does the silly thing by probing the entry point w/o
checking the extension they will attempt to use the extension even
though it cannot work.
That is due our of of an assert which gets removed in release builds.

Simply error out if the extension is not enabled. Thus we can
apply some cleanups with next commits.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>