screenshooter: clean up recorder_binding a little

We already have a pointer to the compositor so change seat->compositor to ec

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/src/screenshooter.c b/src/screenshooter.c
index 4e32db5..fc648a1 100644
--- a/src/screenshooter.c
+++ b/src/screenshooter.c
@@ -564,7 +564,7 @@
 	struct weston_recorder *recorder;
 	static const char filename[] = "capture.wcap";
 
-	wl_list_for_each(output, &seat->compositor->output_list, link) {
+	wl_list_for_each(output, &ec->output_list, link) {
 		listener = wl_signal_get(&output->frame_signal,
 					 weston_recorder_frame_notify);
 		if (listener)