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/include/linux/sched.h b/include/linux/sched.h
index f4e324e..6239bc2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -593,7 +593,7 @@
 #endif
 
 	/* Hash table maintenance information */
-	struct list_head uidhash_list;
+	struct hlist_node uidhash_node;
 	uid_t uid;
 };