ppc4xx: Correct UART input clock calculation and passing to fdt

We now use a value in the gd (global data) structure for the UART input
frequency, since the PPC4xx_SYS_INFO struct is always rewritten completely
in get_sys_info().

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/asm-ppc/global_data.h b/include/asm-ppc/global_data.h
index 4676e2c..05aee74 100644
--- a/include/asm-ppc/global_data.h
+++ b/include/asm-ppc/global_data.h
@@ -107,6 +107,9 @@
 	unsigned int	dp_alloc_base;
 	unsigned int	dp_alloc_top;
 #endif
+#if defined(CONFIG_4xx)
+	u32  uart_clk;
+#endif /* CONFIG_4xx */
 #if defined(CFG_GT_6426x)
 	unsigned int	mirror_hack[16];
 #endif