stdio_names: Ensure MAX_NAMES is defined before use, don't use 3 directly

With tighter build flags the fact that <stdio_dev.h> doesn't have a
reference back to MAX_NAMES causes an error.  Include <stdio.h> here and
then in common/console.c use MAX_NAMES rather than 3 when working with
stdio_names.

Reported-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Tested-by: Peter Robinson <pbrobinson@gmail.com>

include/stdio_dev.h

@@ -8,6 +8,7 @@
 #ifndef _STDIO_DEV_H_
 #define _STDIO_DEV_H_
 
+#include <stdio.h>
 #include <linux/list.h>
 
 /*