lockdep: Fix missing entry in /proc/lock_stat

One entry is missing in the output of /proc/lock_stat.

The cause is, when ls_start() is called the 2nd time, we should
start from stats[@pos-1] but not stats[@pos], because pos == 0
is the header.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <4A88ED15.20800@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>