lightnvm: fix some error code in pblk-init.c

There were a bunch of places in pblk_lines_init() where we didn't set an
error code.  And in pblk_writer_init() we accidentally return 1 instead
of a correct error code, which would result in a Oops later.

Fixes: 11a5d6fdf919 ("lightnvm: physical block device (pblk) target")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@fb.com>