ath9k: rename driver core and hw power save helpers

ath9k_hw_setpower_nolock --> ath9k_hw_setpower()
ath9k_hw_setpower() --> ath9k_setpower()

Also change the param for ath9k_setpower() to pass the ath_softc.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>