ath9k: fix aphy / wiphy idle mismatch

ath9k supports its own set of virtual wiphys, and it uses
the mac80211 idle notifications to know when a device needs
to be idle or not. We recently changed ath9k to force idle
on driver stop() and on resume but forgot to take into account
ath9k's own virtual wiphy idle states. These are used internally
by ath9k to check if the device's radio should be powered down
on each idle call. Without this change its possible that the
device could have been forced off but the virtual wiphy idle
was left on.

Cc: stable@kernel.org
Cc: Paul Stewart <pstew@google.com>
Cc: Amod Bodas <amod.bodas@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>