cfg80211: support configuring vif mac addr on create

This is useful when creating virtual interfaces.
Keeps udev from mucking with things it shouldn't, since
the default MAC is never seen by udev when specified on
the cmd-line during creation.

Signed-off-by: Ben Greear <greearb@candelatech.com>
[check for feature flag in nl80211 to force drivers to set it]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 39d7996..f67948e 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -319,9 +319,12 @@
 /**
  * struct vif_params - describes virtual interface parameters
  * @use_4addr: use 4-address frames
- * @macaddr: address to use for this virtual interface. This will only
- * 	be used for non-netdevice interfaces. If this parameter is set
- * 	to zero address the driver may determine the address as needed.
+ * @macaddr: address to use for this virtual interface.
+ *	If this parameter is set to zero address the driver may
+ *	determine the address as needed.
+ *	This feature is only fully supported by drivers that enable the
+ *	%NL80211_FEATURE_MAC_ON_CREATE flag.  Others may support creating
+ **	only p2p devices with specified MAC.
  */
 struct vif_params {
        int use_4addr;