Staging: rt2860: correct onstack wait_queue_head declaration

Use DECLARE_WAIT_QUEUE_HEAD_ONSTACK to make lockdep happy

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>