locking/mutex: Make mutex::wait_lock raw

The wait_lock of mutex is really a low level lock. Convert it to a
raw_spinlock like the wait_lock of rtmutex.

[ mingo: backmerged the test_lockup.c build fix by bigeasy. ]

Co-developed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211304.166863404@linutronix.de
diff --git a/lib/test_lockup.c b/lib/test_lockup.c
index 864554e..4d93b02f 100644
--- a/lib/test_lockup.c
+++ b/lib/test_lockup.c
@@ -502,7 +502,7 @@ static int __init test_lockup_init(void)
 		       offsetof(rwlock_t, magic),
 		       RWLOCK_MAGIC) ||
 	    test_magic(lock_mutex_ptr,
-		       offsetof(struct mutex, wait_lock.rlock.magic),
+		       offsetof(struct mutex, wait_lock.magic),
 		       SPINLOCK_MAGIC) ||
 	    test_magic(lock_rwsem_ptr,
 		       offsetof(struct rw_semaphore, wait_lock.magic),