Fix various compiler warnings on ppc4xx builds (ELDK 4.0)

Patch by Stefan Roese, 18 Jan 2006
diff --git a/board/esd/hh405/hh405.c b/board/esd/hh405/hh405.c
index 3158803..9c582b1 100644
--- a/board/esd/hh405/hh405.c
+++ b/board/esd/hh405/hh405.c
@@ -590,7 +590,7 @@
 {
 	DECLARE_GLOBAL_DATA_PTR;
 
-	unsigned char str[64];
+	char str[64];
 	int i = getenv_r ("serial#", str, sizeof(str));
 
 	puts ("Board: ");