staging: octeon-usb: use __BITFIELD_FIELD

Use __BITFIELD_FIELD to define bitfields. OCTEON can at least in theory
run also in little-endian mode, so the bitfield definitions should not
assume big-endian byte order.
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>