8250: ratelimit LSR safety check engaged warning.

On my BIOSTAR TA890FXE the ttyS0 ends up spewing:

[904682.485933] ttyS0: LSR safety check engaged!
[904692.505895] ttyS0: LSR safety check engaged!
[904702.525972] ttyS0: LSR safety check engaged!
[904712.545967] ttyS0: LSR safety check engaged!
[904722.566125] ttyS0: LSR safety check engaged!
..
lets limit it so it won't be the only thing visible
in the ring buffer.

CC: Alan Cox <alan@linux.intel.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/8250.c

@@ -2055,8 +2055,8 @@ static int serial8250_startup(struct uart_port *port)
 	 */
 	if (!(up->port.flags & UPF_BUGGY_UART) &&
 	    (serial_inp(up, UART_LSR) == 0xff)) {
-		printk(KERN_INFO "ttyS%d: LSR safety check engaged!\n",
-		       serial_index(&up->port));
+		printk_ratelimited(KERN_INFO "ttyS%d: LSR safety check engaged!\n",
+				   serial_index(&up->port));
 		return -ENODEV;
 	}