[PATCH][RT] spinlock: Add include for BUG() in spinlock_rt.h

[Steven Rostedt <rostedt@goodmis.org>]

spinlock_rt.h references BUG(), but it does not include bug.h, and on
some architectures (powerpc) this can cause a build failure.

Reported-by: Iratxo Pichel Ortiz <ipichel@albentia.com>
Reported-by: leroy christophe <christophe.leroy@c-s.fr>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
----
[ Thomas, can you add this patch to your queue so that I can add it to
stable. Please, let me know when you have. Thanks! ]

diff --git a/include/linux/spinlock_rt.h b/include/linux/spinlock_rt.h
index 3b555b4..0618387 100644
--- a/include/linux/spinlock_rt.h
+++ b/include/linux/spinlock_rt.h
@@ -5,6 +5,8 @@
 #error Do not include directly. Use spinlock.h
 #endif
 
+#include <linux/bug.h>
+
 extern void
 __rt_spin_lock_init(spinlock_t *lock, char *name, struct lock_class_key *key);