lockdep: Improve the readibility of crossrelease related splats

When a crossrelease related deadlock is detected in a commit, the
current implemention makes splats like:

> fsck.ext4/148 is trying to acquire lock:
>  (&bdev->bd_mutex){+.+.}, at: [<ffffffff8116e73e>] __blkdev_put+0x33/0x190
>
>  but now in release context of a crosslock acquired at the following:
>  ((complete)&wait#2){+.+.}, at: [<ffffffff812159e0>] blk_execute_rq+0xbb/0xda
>
>  which lock already depends on the new lock.
> ...

However, it could be misleading because the current task has got the
lock already, and in fact the deadlock is detected when it is doing the
commit of the crossrelease lock. So make the splats more accurate to
describe the deadlock case.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>