libweston: remove unused backend_init() arguments

Backends do not have access to command line elements nor weston_config
anymore. They use the backend-specific config APIs now.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Giulio Camuffo <giuliocamuffo@gmail.com>
diff --git a/src/compositor.c b/src/compositor.c
index 682357b..07874f6 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -4885,13 +4885,11 @@
 			       struct weston_backend_config *config_base)
 {
 	int (*backend_init)(struct weston_compositor *c,
-			    int *argc, char *argv[],
-			    struct weston_config *config,
 			    struct weston_backend_config *config_base);
 
 	backend_init = weston_load_module(backend, "backend_init");
 	if (!backend_init)
 		return -1;
 
-	return backend_init(compositor, NULL, NULL, NULL, config_base);
+	return backend_init(compositor, config_base);
 }