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>
8 files changed