lockdep: Add novalidate class for dev->mutex conversion

The conversion of device->sem to device->mutex resulted in lockdep
warnings. Create a novalidate class for now until the driver folks
come up with separate classes. That way we have at least the basic
mutex debugging coverage.

Add a checkpatch error so the usage is reserved for device->mutex.

[ tglx: checkpatch and compile fix for LOCKDEP=n ]

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index ec21304..5428679 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2711,6 +2711,8 @@
 }
 EXPORT_SYMBOL_GPL(lockdep_init_map);
 
+struct lock_class_key __lockdep_no_validate__;
+
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
  * We maintain the dependency maps and validate the locking attempt:
@@ -2745,6 +2747,9 @@
 		return 0;
 	}
 
+	if (lock->key == &__lockdep_no_validate__)
+		check = 1;
+
 	if (!subclass)
 		class = lock->class_cache;
 	/*