lockdep: Silence warning if CONFIG_LOCKDEP isn't set

Since commit c9a49628 ("nfsd:
make client_lock per net") compiling nfs4state.o without
CONFIG_LOCKDEP set, triggers this GCC warning:

    fs/nfsd/nfs4state.c: In function ‘free_client’:
    fs/nfsd/nfs4state.c:1051:19: warning: unused variable ‘nn’ [-Wunused-variable]

The cause of that warning is that lockdep_assert_held() compiles
away if CONFIG_LOCKDEP is not set. Silence this warning by using
the argument to lockdep_assert_held() as a nop if CONFIG_LOCKDEP
is not set.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Link: http://lkml.kernel.org/r/1359060797.1325.33.camel@x61.thuisdomeinSigned-off-by: Ingo Molnar <mingo@kernel.org>
--
 include/linux/lockdep.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

include/linux/lockdep.h

@@ -410,7 +410,7 @@ struct lock_class_key { };
 
 #define lockdep_depth(tsk)	(0)
 
-#define lockdep_assert_held(l)			do { } while (0)
+#define lockdep_assert_held(l)			do { (void)(l); } while (0)
 
 #define lockdep_recursing(tsk)			(0)