[SERIAL] Support Au1x00 8250 UARTs using the generic 8250 driver.

The offsets of the registers are in a different place, and
some parts cannot handle a full set of modem control signals.

Signed-off-by: Pantelis Antoniou <pantelis@embeddedalley.ocm>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/linux/serial_8250.h

@@ -42,6 +42,7 @@ enum {
 	PLAT8250_DEV_BOCA,
 	PLAT8250_DEV_HUB6,
 	PLAT8250_DEV_MCA,
+	PLAT8250_DEV_AU1X00,
 };
 
 /*