Port cmos.default handling to C environment bootblock

Gather related code in the new file drivers/pc80/rtc/mc146818rtc_boot.c,
call sanitize_cmos() from C environment bootblock.

Change-Id: Ia5c64de208a5986299c0508d0e11eeb8473deef1
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20768
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/lib/bootblock.c

@@ -36,6 +36,7 @@ asmlinkage void bootblock_main_with_timestamp(uint64_t base_timestamp)
 	if (IS_ENABLED(CONFIG_COLLECT_TIMESTAMPS) && _timestamp_size > 0)
 		timestamp_init(base_timestamp);
 
+	sanitize_cmos();
 	cmos_post_init();
 
 	bootblock_soc_early_init();