ieee802154: add several phy supported handling

This patch adds support for phy supported handling for all other already
existing handling 802.15.4 functionality. We assume now a fully 802.15.4
complaint transceiver at phy allocation. If a transceiver can support
802.15.4 default values only, then the values should be overwirtten by
values the transceiver supports. If the transceiver doesn't set the
according hardware flags, we assume the 802.15.4 defaults now which
cannot be changed.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Suggested-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>