ieee802154: setting extended address while iface add

This patch adds support for setting an extended address while
registration a new interface. If ieee802154_is_valid_extended_addr
getting as parameter and invalid extended address then the perm address
is fallback. This is useful to make some default handling while for
example default registration of a wpan interface while phy registration.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>