[POWERPC] fix showing xmon help

In some configuration, xmon help string is larger than xmon_printf
buffer.  We need not to use printf.  This patch adds xmon_puts and
change to use it to show help string.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/xmon/nonstdio.h

@@ -5,6 +5,7 @@
 
 extern int xmon_putchar(int c);
 extern int xmon_getchar(void);
+extern void xmon_puts(const char *);
 extern char *xmon_gets(char *, int);
 extern void xmon_printf(const char *, ...);
 extern void xmon_map_scc(void);