ppc4xx: Use common NS16550 driver for PPC4xx UART

This patch removes the PPC4xx UART driver. Instead the common NS16550
driver is used, since all PPC4xx SoC's use this peripheral device.

The file 4xx_uart.c now only implements the UART clock calculation
function which also sets the SoC internal UART divisors.

All PPC4xx board config headers are changed to use this common NS16550
driver now.

Tested on these boards:
acadia, canyonlands, katmai, kilauea, sequoia, zeus

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/amcc-common.h b/include/configs/amcc-common.h
index 23a859f..9c53d37 100644
--- a/include/configs/amcc-common.h
+++ b/include/configs/amcc-common.h
@@ -31,8 +31,12 @@
 /*
  * UART
  */
-#define CONFIG_BAUDRATE		115200
 #define CONFIG_SERIAL_MULTI
+#define CONFIG_SYS_NS16550
+#define CONFIG_SYS_NS16550_SERIAL
+#define CONFIG_SYS_NS16550_REG_SIZE	1
+#define CONFIG_SYS_NS16550_CLK		get_serial_clock()
+#define CONFIG_BAUDRATE		115200
 #define CONFIG_SYS_BAUDRATE_TABLE  \
     {300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400}