mac80211: support P2P Device abstraction

After cfg80211 got a P2P Device abstraction, add
support to mac80211. Whether it really is supported
or not will depend on whether or not the driver has
support for it, but mac80211 needs to change to be
able to support drivers that need a P2P Device.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index a81154d..da9003b 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -9,7 +9,7 @@
 {
 	WARN(!(sdata->flags & IEEE80211_SDATA_IN_DRIVER),
 	     "%s:  Failed check-sdata-in-driver check, flags: 0x%x\n",
-	     sdata->dev->name, sdata->flags);
+	     sdata->dev ? sdata->dev->name : sdata->name, sdata->flags);
 }
 
 static inline struct ieee80211_sub_if_data *