plist: fix PLIST_NODE_INIT to work with debug enabled

It seems that PLIST_NODE_INIT breaks if used and DEBUG_PI_LIST is defined.
Since there are no current users of PLIST_NODE_INIT, this has gone
undetected.  This patch fixes the build issue that enables the
DEBUG_PI_LIST later in the series when we use it in init_task.h

Signed-off-by: Gregory Haskins <ghaskins@novell.com>

include/linux/plist.h

@@ -96,15 +96,18 @@ struct plist_node {
 # define PLIST_HEAD_LOCK_INIT(_lock)
 #endif
 
+#define _PLIST_HEAD_INIT(head)				\
+	.prio_list = LIST_HEAD_INIT((head).prio_list),	\
+	.node_list = LIST_HEAD_INIT((head).node_list)
+
 /**
  * PLIST_HEAD_INIT - static struct plist_head initializer
  * @head:	struct plist_head variable name
  * @_lock:	lock to initialize for this list
  */
 #define PLIST_HEAD_INIT(head, _lock)			\
 {							\
-	.prio_list = LIST_HEAD_INIT((head).prio_list),	\
-	.node_list = LIST_HEAD_INIT((head).node_list),	\
+        _PLIST_HEAD_INIT(head),                         \
 	PLIST_HEAD_LOCK_INIT(&(_lock))			\
 }
 
@@ -116,7 +119,7 @@ struct plist_node {
 #define PLIST_NODE_INIT(node, __prio)			\
 {							\
 	.prio  = (__prio),				\
-	.plist = PLIST_HEAD_INIT((node).plist, NULL),	\
+	.plist = { _PLIST_HEAD_INIT((node).plist) }, 	\
 }
 
 /**