Add const to 'field' argument of rt2x00usb_regbusy_read()
(all arguments match rt2x00pci_regbusy_read() ones now).
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Acked-by: NIvo van Doorn <IvDoorn@gmail.com>
Acked-by: NGertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>