mac80211: do remain-on-channel while idle

The IDLE handling in HW off-channel is broken right
now since we turn off IDLE only when the off-channel
period already started. Therefore, all drivers that
use it today (only iwlwifi!) must support off-channel
while idle, so playing with idle isn't needed at all.

Off-channel in general, since it's no longer used for
authentication/association, shouldn't affect PS, so
also remove that logic.

Also document a small caveat for reporting TX status
from off-channel frames in HW remain-on-channel.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index d2ed86d..6e700bf 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -2183,7 +2183,13 @@
  *	offload. Frames to transmit on the off-channel channel are transmitted
  *	normally except for the %IEEE80211_TX_CTL_TX_OFFCHAN flag. When the
  *	duration (which will always be non-zero) expires, the driver must call
- *	ieee80211_remain_on_channel_expired(). This callback may sleep.
+ *	ieee80211_remain_on_channel_expired().
+ *	The driver must not call ieee80211_remain_on_channel_expired() before
+ *	the TX status for a frame that was sent off-channel, otherwise the TX
+ *	status is reported to userspace in an invalid way.
+ *	Note that this callback may be called while the device is in IDLE and
+ *	must be accepted in this case.
+ *	This callback may sleep.
  * @cancel_remain_on_channel: Requests that an ongoing off-channel period is
  *	aborted before it expires. This callback may sleep.
  *