serial: 8250: 8250_core: Use dev_name() during request_irq()

Passing "serial" as name during request_irq() results in all serial port
irqs have same name. This does not help much to easily identify which
irq belongs to which serial port instance. Therefore pass dev_name()
during request_irq() so that better identifiable name is listed for
serial ports in cat /proc/interrupts output.

Output of cat /proc/interrupts
Before this patch:
 26:        689          0     GICv2 309 Edge      serial
After this patch:
 26:        696          0     GICv2 309 Edge      2530c00.serial

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>