[SERIAL] Arrange better identification of ports

Folk seem to get confused when they see two or more ttyS0 ports
appearing at boot time.  One comes from the legacy table, and
one from PNP.

Hence, display the bus ID of the device which supplied the port.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/serial_core.c

@@ -1967,7 +1967,9 @@ uart_report_port(struct uart_driver *drv, struct uart_port *port)
 		break;
 	}
 
-	printk(KERN_INFO "%s%d at %s (irq = %d) is a %s\n",
+	printk(KERN_INFO "%s%s%s%d at %s (irq = %d) is a %s\n",
+	       port->dev ? port->dev->bus_id : "",
+	       port->dev ? ": " : "",
 	       drv->dev_name, port->line, address, port->irq, uart_type(port));
 }