lightnvm: pblk: fix chunk close trace event check

The check for chunk closes suffers from an off-by-one issue, leading
to chunk close events not being traced.

Fixes: 4c44abf4 ("lightnvm: pblk: add trace events for chunk states")
Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>