mainboard: Remove use of IFD_BIOS_START/IFD_BIOS_END

BUG=chrome-os-partner:54563

Change-Id: If07710333cbb84ce70d6d4fa40602a74c898c08a
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15293
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
3 files changed