usb: storage: shuttle_usbat: fix sparse warning

Fix the following sparse warning:

| drivers/usb/storage/shuttle_usbat.c:173:22: warning:
|	symbol 'usbat_usb_ids' was not declared. Should
|	it be static?
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/storage/shuttle_usbat.c

@@ -170,7 +170,7 @@ static int init_usbat_flash(struct us_data *us);
 { USB_DEVICE_VER(id_vendor, id_product, bcdDeviceMin, bcdDeviceMax), \
   .driver_info = (flags)|(USB_US_TYPE_STOR<<24) }
 
-struct usb_device_id usbat_usb_ids[] = {
+static struct usb_device_id usbat_usb_ids[] = {
 #	include "unusual_usbat.h"
 	{ }		/* Terminating entry */
 };