lightnvm: pblk: fix lock order in pblk_rb_tear_down_check

In pblk_rb_tear_down_check() the spinlock functions are not
called in proper order.

Fixes: a4bd217 ("lightnvm: physical block device (pblk) target")
Signed-off-by: Igor Konopko <[e-mail]>
Reviewed-by: Javier González <[e-mail]>
Reviewed-by: Hans Holmberg <[e-mail]>
Signed-off-by: Matias Bjørling <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/lightnvm/pblk-rb.c

···
 	}
 
 out:
-	spin_unlock(&rb->w_lock);
 	spin_unlock_irq(&rb->s_lock);
+	spin_unlock(&rb->w_lock);
 
 	return ret;
 }