ath9k: rework power state handling

Turning off the radio when mac80211 tells the driver that it's idle is not
a good idea, as idle interfaces might still occasionally scan or send packets.
The only time the radio can be safely turned off is when drv_stop has been
called. In the mean time, use sc->ps_idle only to indicate network sleep vs
full sleep.
Move the LED GPIO changes out of the PCI suspend/resume path, the start/stop
functions already take care of that.

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