We should not be idle when we get the ATH9K_INT_TIM_TIMER,
otherwise its a sign of something broken in our design with
our idle state machine and mac80211. Skip these and WARN once
just in case this is triggerable.

Cc: Paul Stewart <pstew@google.com>
Cc: Amod Bodas <amod.bodas@atheros.com>
signed-off-by: NLuis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>