nbd: lower the loglevel of an error message

This is only an error, no need to use KERN_CRIT log level.
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Paul Clements <Paul.Clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

drivers/block/nbd.c

@@ -745,7 +745,7 @@ static int __init nbd_init(void)
 	BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 
 	if (max_part < 0) {
-		printk(KERN_CRIT "nbd: max_part must be >= 0\n");
+		printk(KERN_ERR "nbd: max_part must be >= 0\n");
 		return -EINVAL;
 	}