lightnvm: pblk: set propper line as data_line after gc

In current implementation of l2p recovery, when we are after gc and we
have open line, we are not setting current data line properly (we set
last line from the device instead of last line ordered by seq_nr) and
in consequence, kernel panic and data corruption.

Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@intel.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>