usb: storage: isd200: fix sparse warning

Fix the following sparse warning:

| drivers/usb/storage/freecom.c:122:22: warning: symbol
|	'freecom_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/isd200.c

@@ -76,7 +76,7 @@ static int isd200_Initialization(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 isd200_usb_ids[] = {
+static struct usb_device_id isd200_usb_ids[] = {
 #	include "unusual_isd200.h"
 	{ }		/* Terminating entry */
 };