Staging: rt2870: add ID for Sitecom WL-315

Signed-off-by: Daniele Napolitano <dnax88@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>