powerpc/perf/24x7: use rb_entry

To make the code clearer, use rb_entry() instead of container_of() to
deal with rbtree.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/perf/hv-24x7.c

@@ -571,7 +571,7 @@ static int event_uniq_add(struct rb_root *root, const char *name, int nl,
 		struct event_uniq *it;
 		int result;
 
-		it = container_of(*new, struct event_uniq, node);
+		it = rb_entry(*new, struct event_uniq, node);
 		result = ev_uniq_ord(name, nl, domain, it->name, it->nl,
 					it->domain);