Gigabeat S has no need for a USB tick. Put in a simple framework that allows USB monitoring by event. Also add a couple missed usb_enable calls when the connection is not for 'slave mode'.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19768 a1c6a512-1295-4272-9138-f99709370657

firmware/target/arm/imx31/gigabeat-s/usb-imx31.c

@@ -59,6 +59,7 @@ void usb_connect_event(void)
         USB_INSERTED : USB_EXTRACTED;
     /* Notify power that USB charging is potentially available */
     charger_usb_detect_event(usb_status);
+    usb_status_event(usb_status);
 }
 
 int usb_detect(void)

firmware/target/arm/imx31/gigabeat-s/usb-target.h

@@ -25,6 +25,9 @@
 #define USB_DRIVER_CLOSE
 #endif
 
+/* Connect by events, not by tick polling */
+#define USB_STATUS_BY_EVENT
+
 void usb_connect_event(void);
 void usb_init_device(void);
 int usb_detect(void);