ath9k: fix a regression in ath9k_ps_restore

After 'ath9k: optimize ath9k_ps_restore', it would only send the device to
network sleep and not to full sleep anymore, potentially causing more
battery drain.

Reported-by: Vivek Natarajan <nataraja@qca.qualcomm.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>