drivers/pc80/rtc: Reorganize prototypes

Change-Id: Idea18f437c31ebe83dd61a185e614106a1f8f976
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38199
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/arch/x86/post.c b/src/arch/x86/post.c
index 0aaf9b7..ec185c7 100644
--- a/src/arch/x86/post.c
+++ b/src/arch/x86/post.c
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /* This file is part of the coreboot project. */
 
+#include <post.h>
 #include <stdint.h>
 #include <console/console.h>
 #include <arch/io.h>