[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.c

@@ -132,3 +132,8 @@ void xmon_printf(const char *format, ...)
 	va_end(args);
 	xmon_write(xmon_outbuf, n);
 }
+
+void xmon_puts(const char *str)
+{
+	xmon_write(str, strlen(str));
+}