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>

src/arch/x86/cpu.c

@@ -5,6 +5,7 @@
 #include <boot/coreboot_tables.h>
 #include <console/console.h>
 #include <cpu/cpu.h>
+#include <post.h>
 #include <string.h>
 #include <cpu/x86/mp.h>
 #include <cpu/x86/lapic.h>