mac80211: mesh gate fixes

Since a v1 of the mesh gate series was accidentally applied, this patch
contains the changes in v2.

These are:
	- automatically make mesh gate a root node.
	- use TU_TO_EXP_TIME macro.
	- initialize timer instead of checking for NULL timer function.
	- cleanups.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 1c4f53c..28ab510 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -537,8 +537,8 @@
 
 	mesh_path_tx_root_frame(sdata);
 	mod_timer(&ifmsh->mesh_path_root_timer,
-		  round_jiffies(jiffies +
-			  usecs_to_jiffies(ifmsh->mshcfg.dot11MeshHWMPRannInterval * 1024)));
+		  round_jiffies(TU_TO_EXP_TIME(
+				  ifmsh->mshcfg.dot11MeshHWMPRannInterval)));
 }
 
 #ifdef CONFIG_PM