ieee802154: introduce wpan_phy_supported

This patch introduce the wpan_phy_supported struct for wpan_phy. There
is currently no way to check if a transceiver can handle IEEE 802.15.4
complaint values. With this struct we can check before if the
transceiver supports these values before sending to driver layer.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Suggested-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Acked-by: Varka Bhadram <varkabhadram@gmail.com>
Cc: Alan Ott <alan@signal11.us>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>