include: Move snprintf to stdio.h

Move snprintf to stdio.h since it is needed by exteranl libraries.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

lib/display_options.c

@@ -12,6 +12,7 @@
 #include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <asm/io.h>
+#include <stdio.h>
 #include <vsprintf.h>
 
 char *display_options_get_banner_priv(bool newlines, const char *build_tag,