staging: octeon-usb: remove useless prefix from internal routines

Original CVMX code used "__" to distinguis internal USB functions
from public ones. But in Linux all cvmx_usb routines are internal
to this driver, so such separation is useless.
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>