Convert uid hash to hlist

Surprisingly, but (spotted by Alexey Dobriyan) the uid hash still uses
list_heads, thus occupying twice as much place as it could.  Convert it to
hlist_heads.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 85af942..e7ba1bf 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -39,7 +39,7 @@
 	kref_init(&ns->kref);
 
 	for (n = 0; n < UIDHASH_SZ; ++n)
-		INIT_LIST_HEAD(ns->uidhash_table + n);
+		INIT_HLIST_HEAD(ns->uidhash_table + n);
 
 	/* Insert new root user.  */
 	ns->root_user = alloc_uid(ns, 0);