8250_pci: Fix kernel panic when pch_uart is disabled

Currently, ".setup" function is not set.
As a result, when detecting our IOH's uart device without pch_uart, kernel panic
occurs at the following of pciserial_init_ports().

	for (i = 0; i < nr_ports; i++) {
		if (quirk->setup(priv, board, &serial_port, i))
			break;

So, this patch adds the ".setup" function.
We can use pci_default_setup because our IOH's uart is compatible with 16550.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.lapis-semi.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>