lockdep: fix a typo in the __lock_acquire comment

Fix a typo in the __lock_acquire comment.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>