'blks' is malloced in pblk_bb_discovery() and should be freed
before leaving from the nvm_get_tgt_bb_tbl() error handling cases,
otherwise it will cause memory leak. Also skip assign blks to
rlun->bb_list when error.

Fixes: a4bd217b ("lightnvm: physical block device (pblk) target")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NJens Axboe <axboe@fb.com>