serial: 8250: 8250_core: Fix irq name for 8250 serial IRQ

Using dev_name() as IRQ name during request_irq() might be misleading in
case of serial over PCI. Therefore identify serial port IRQ using
uart_port's name field. This will help mapping IRQs to appropriate
ttySN(where N is the serial port index) instances.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>