[POWERPC] Make xmon_write accept a const buffer

Because xmon_write doesn't change the buffer, we should add 'const'
qualifier to the argument which points it.
Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/xmon/nonstdio.h

@@ -9,6 +9,6 @@ extern char *xmon_gets(char *, int);
 extern void xmon_printf(const char *, ...);
 extern void xmon_map_scc(void);
 extern int xmon_expect(const char *str, unsigned long timeout);
-extern int xmon_write(void *ptr, int nb);
+extern int xmon_write(const void *ptr, int nb);
 extern int xmon_readchar(void);
 extern int xmon_read_poll(void);

arch/powerpc/xmon/start.c

@@ -14,7 +14,7 @@ void xmon_map_scc(void)
 {
 }
 
-int xmon_write(void *ptr, int nb)
+int xmon_write(const void *ptr, int nb)
 {
 	return udbg_write(ptr, nb);
 }