gui: avoid high CPU usage while waiting for input

- add a timeout to ev_get
- set timeout to 1 second when idle
- delay timeout for 15 frames to keep animation objects working
- stop kinetic scrolling immediately at end of list

Change-Id: I77138055c464b65b71e296f9c7ef63ea06809bc1
diff --git a/minuitwrp/minui.h b/minuitwrp/minui.h
index abebc14..3aa4865 100644
--- a/minuitwrp/minui.h
+++ b/minuitwrp/minui.h
@@ -75,7 +75,7 @@
 
 int ev_init(void);
 void ev_exit(void);
-int ev_get(struct input_event *ev);
+int ev_get(struct input_event *ev, int timeout_ms);
 int ev_has_mouse(void);
 
 // Resources