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/ORSG.h b/include/configs/ORSG.h
index 1424713..3d35362 100644
--- a/include/configs/ORSG.h
+++ b/include/configs/ORSG.h
@@ -105,6 +105,12 @@
 #define CONFIG_SYS_MEMTEST_START	0x0400000	/* memtest works on	*/
 #define CONFIG_SYS_MEMTEST_END		0x0C00000	/* 4 ... 12 MB in DRAM	*/
 
+#define CONFIG_CONS_INDEX	1	/* Use UART0			*/
+#define CONFIG_SYS_NS16550
+#define CONFIG_SYS_NS16550_SERIAL
+#define CONFIG_SYS_NS16550_REG_SIZE	1
+#define CONFIG_SYS_NS16550_CLK		get_serial_clock()
+
 #undef	CONFIG_SYS_EXT_SERIAL_CLOCK	       /* no external serial clock used */
 #define CONFIG_SYS_BASE_BAUD	    691200