ath9k: add missing ps wakeup/restore calls

There are several places where ath_reset() was called without proper
calls to ath9k_ps_wakeup/ath9k_ps_restore. To fix this, add those calls
directly to ath_reset and drop them from callers where it makes sense.

Also add them to the config callback around ath_update_txpow to fix a
crash that happens when the tx power changed before any vif is brought up.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>