cfg80211: add P2P Device abstraction

In order to support using a different MAC address
for the P2P Device address we must first have a
P2P Device abstraction that can be assigned a MAC
address.

This abstraction will also be useful to support
offloading P2P operations to the device, e.g.
periodic listen for discoverability.

Currently, the driver is responsible for assigning
a MAC address to the P2P Device, but this could be
changed by allowing a MAC address to be given to
the NEW_INTERFACE command.

As it has no associated netdev, a P2P Device can
only be identified by its wdev identifier but the
previous patches allowed using the wdev identifier
in various APIs, e.g. remain-on-channel.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 7dff94e..9a4e4e3 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1390,6 +1390,8 @@
 		case NL80211_IFTYPE_MONITOR:
 			/* ignore virtual */
 			break;
+		case NL80211_IFTYPE_P2P_DEVICE:
+			/* not yet supported */
 		case NL80211_IFTYPE_UNSPECIFIED:
 		case NUM_NL80211_IFTYPES:
 		case NL80211_IFTYPE_P2P_CLIENT: