Increase MAX_FILES to 128

I already hit the limit while doing DFU on a custom board. Increase the
value to a safe limit.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

include/stdio.h

@@ -49,7 +49,7 @@ int	vsnprintf(char *buf, size_t size, const char *fmt, va_list args);
 #define stdin		0
 #define stdout		1
 #define stderr		2
-#define MAX_FILES	16
+#define MAX_FILES	128
 
 void	fprintf(int file, const char *fmt, ...);
 int	fputs(int file, const char *s);