ieee802154: rename struct ieee802154_addr to *_sa

The struct as currently defined uses host byte order for some fields,
and most big endian/EUI display byte order for other fields. Inside the
stack, endianness should ideally match network byte order where possible
to minimize the number of byteswaps done in critical paths, but this
patch does not address this; it is only preparatory.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>