mac80211: document sleep requirements for channel context ops

Channel context driver operations can sleep, so add might_sleep()
and document this.

Signed-off-by: Chaitanya T K <chaitanya.mgit@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index dac575c..82045fc 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -3172,18 +3172,24 @@
  *	The callback is optional and can sleep.
  *
  * @add_chanctx: Notifies device driver about new channel context creation.
+ *	This callback may sleep.
  * @remove_chanctx: Notifies device driver about channel context destruction.
+ *	This callback may sleep.
  * @change_chanctx: Notifies device driver about channel context changes that
  *	may happen when combining different virtual interfaces on the same
  *	channel context with different settings
+ *	This callback may sleep.
  * @assign_vif_chanctx: Notifies device driver about channel context being bound
  *	to vif. Possible use is for hw queue remapping.
+ *	This callback may sleep.
  * @unassign_vif_chanctx: Notifies device driver about channel context being
  *	unbound from vif.
+ *	This callback may sleep.
  * @switch_vif_chanctx: switch a number of vifs from one chanctx to
  *	another, as specified in the list of
  *	@ieee80211_vif_chanctx_switch passed to the driver, according
  *	to the mode defined in &ieee80211_chanctx_switch_mode.
+ *	This callback may sleep.
  *
  * @start_ap: Start operation on the AP interface, this is called after all the
  *	information in bss_conf is set and beacon can be retrieved. A channel