ath5k_config updates the software context without taking sc->lock.

Changes-licensed-under: 3-Clause-BSD
Signed-off-by: NBob Copeland <me@bobcopeland.com>
Acked-by: NNick Kossifidis <mickflemm@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>