serial: 8250: add support for ACPI-probed serial port for X-Gene platform

Enable APM X-Gene SoC serial port functionality when using ACPI table to
initialize serial port.

Signed-off-by: Feng Kan <fkan@apm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dw.c

@@ -351,10 +351,20 @@ static int dw8250_probe_of(struct uart_port *p,
 static int dw8250_probe_acpi(struct uart_8250_port *up,
 			     struct dw8250_data *data)
 {
+	const struct acpi_device_id *id;
 	struct uart_port *p = &up->port;
 
 	dw8250_setup_port(up);
 
+	id = acpi_match_device(p->dev->driver->acpi_match_table, p->dev);
+	if (!id)
+		return -ENODEV;
+
+	if (!p->uartclk)
+		if (device_property_read_u32(p->dev, "clock-frequency",
+					     &p->uartclk))
+			return -EINVAL;
+
 	p->iotype = UPIO_MEM32;
 	p->serial_in = dw8250_serial_in32;
 	p->serial_out = dw8250_serial_out32;
@@ -577,6 +587,7 @@ static const struct acpi_device_id dw8250_acpi_match[] = {
 	{ "INT3435", 0 },
 	{ "80860F0A", 0 },
 	{ "8086228A", 0 },
+	{ "APMC0D08", 0},
 	{ },
 };
 MODULE_DEVICE_TABLE(acpi, dw8250_acpi_match);