pf: add error handling support for add_disk()

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/paride/pf.c

@@ -962,7 +962,9 @@ static int __init pf_init_unit(struct pf_unit *pf, bool autoprobe, int port,
 	if (pf_probe(pf))
 		goto out_pi_release;
 
-	add_disk(disk);
+	ret = add_disk(disk);
+	if (ret)
+		goto out_pi_release;
 	pf->present = 1;
 	return 0;