lockdep: build fix

fix:

 kernel/built-in.o: In function `lockdep_stats_show':
 lockdep_proc.c:(.text+0x3cb2f): undefined reference to `lockdep_count_forward_deps'
 kernel/built-in.o: In function `l_show':
 lockdep_proc.c:(.text+0x3d02b): undefined reference to `lockdep_count_forward_deps'
 lockdep_proc.c:(.text+0x3d047): undefined reference to `lockdep_count_backward_deps'

Signed-off-by: Ingo Molnar <mingo@elte.hu>