lockdep: Fix typos in documentation

s/head/held

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <4A7BD37E.9060806@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 file changed