ieee802154: atusb: Driver for Busware HUL dongle

Busware manufactured an USB dongle that is quite similar to
the atben and rzusb USB dongles. that are already supported.
This patch aims to support the Busware HUL dongle (called
hulusb) alongside atusb and rzusb. hulusb is using the
at86rf212 transceiver which is specifically designed to
support the 700/800/900 MHz wave band.

The source code is heavily inspired by the existing atusb
and at86rf2xx drivers.

Signed-off-by: Josef Filzmaier <j.filzmaier@gmx.at>
Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>