[RBTREE] Update hrtimers to use rb_parent() accessor macro.

Also switch it to use the same method of using off-tree nodes as
everyone else now does -- set them to point to themselves.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index d2a7296..04ab27d 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -393,7 +393,7 @@
 	if (base->first == &timer->node)
 		base->first = rb_next(&timer->node);
 	rb_erase(&timer->node, &base->active);
-	timer->node.rb_parent = HRTIMER_INACTIVE;
+	rb_set_parent(&timer->node, &timer->node);
 }
 
 /*
@@ -578,7 +578,7 @@
 		clock_id = CLOCK_MONOTONIC;
 
 	timer->base = &bases[clock_id];
-	timer->node.rb_parent = HRTIMER_INACTIVE;
+	rb_set_parent(&timer->node, &timer->node);
 }
 
 /**