md: don't check 'mddev->pers' and 'pers->quiesce' from suspend_lo_store()

Now that mddev_suspend() doean't rely on 'mddev->pers' to be set, it's
safe to remove such checking.

This will also allow the array to be suspended even before the array
is ran.

Signed-off-by: Yu Kuai <[e-mail]>
Signed-off-by: Song Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/md/md.c

···
 	err = mddev_lock(mddev);
 	if (err)
 		return err;
-	err = -EINVAL;
-	if (mddev->pers == NULL ||
-	    mddev->pers->quiesce == NULL)
-		goto unlock;
+
 	mddev_suspend(mddev);
 	mddev->suspend_lo = new;
 	mddev_resume(mddev);
 
-	err = 0;
-unlock:
 	mddev_unlock(mddev);
-	return err ?: len;
+	return len;
 }
 static struct md_sysfs_entry md_suspend_lo =
 __ATTR(suspend_lo, S_IRUGO|S_IWUSR, suspend_lo_show, suspend_lo_store);