The key instead of address of lock_class should be output in
/proc/lockdep when forward dependency is output, because key is
output for lock_class itself as identifier too.

This patch is based on x86/auto-latest branch of git-x86 tree, and has
been tested on x86_64 platform.
Signed-off-by: NHuang Ying <ying.huang@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>