mac80211: move sdata debugfs dir to vif

There is need create driver own per interface debugfs files. This is
currently done by drv_{add,remove}_interface_debugfs() callbacks. But it
is possible that after we remove interface from the driver (i.e.
on suspend) we call drv_remove_interface_debugfs() function. Fixing this
problem will require to add call drv_{add,remove}_interface_debugfs()
anytime we create and remove interface in mac80211. So it's better to
add debugfs dir dentry to vif structure to allow to create/remove
custom debugfs driver files on drv_{add,remove}_interface().

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -1067,6 +1067,9 @@ enum ieee80211_vif_flags {
  *	path needing to access it; even though the netdev carrier will always
  *	be off when it is %NULL there can still be races and packets could be
  *	processed after it switches back to %NULL.
+ * @debugfs_dir: debugfs dentry, can be used by drivers to create own per
+ *      interface debug files. Note that it will be NULL for the virtual
+ *	monitor interface (if that is requested.)
  * @drv_priv: data area for driver use, will always be aligned to
  *	sizeof(void *).
  */
@@ -1083,6 +1086,10 @@ struct ieee80211_vif {
 
 	u32 driver_flags;
 
+#ifdef CONFIG_MAC80211_DEBUGFS
+	struct dentry *debugfs_dir;
+#endif
+
 	/* must be last */
 	u8 drv_priv[0] __aligned(sizeof(void *));
 };