ipack/devices/ipoctal: don't check if nb_bytes is < 0

It is an unsigned int so that check is pointless.

Signed-off-by: Alberto Garcia <agarcia@igalia.com>
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>