input: Move weston_seat_set_keyboard_focus and document

Place it with the other weston_seat functions.

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/libweston/compositor.h b/libweston/compositor.h
index 5701a05..49ef063 100644
--- a/libweston/compositor.h
+++ b/libweston/compositor.h
@@ -1167,9 +1167,6 @@
 weston_spring_done(struct weston_spring *spring);
 
 void
-weston_seat_set_keyboard_focus(struct weston_seat *seat,
-			       struct weston_surface *surface);
-void
 notify_motion(struct weston_seat *seat, uint32_t time,
 	      struct weston_pointer_motion_event *event);
 void
@@ -1717,6 +1714,10 @@
 struct weston_touch *
 weston_seat_get_touch(struct weston_seat *seat);
 
+void
+weston_seat_set_keyboard_focus(struct weston_seat *seat,
+			       struct weston_surface *surface);
+
 #ifdef  __cplusplus
 }
 #endif