When multiple backends are loaded simultaneously, they all have
to register their own head change notification listener and
output configuration callback.
To avoid calling output configuration for heads created by other
backends, only iterate over heads that were created from the given
backend by comparing the weston_head::backend pointer to the one
stored in the head change notification listener.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
69679b271f