mainboard/intel: add leafhill board directory

This commit adds the initial scaffolding for the Intel Leafhill CRB
with Apollo Lake silicon.

The google/reef directory is used as a template. This commit only
makes the minimum changes to Kconfig and Kconfig.name needed for
the build bot to not have issues.

Change-Id: I088edee0e94ecfb4666fa31e08dbcfd24a81891b
Signed-off-by: Brenton Dong <brenton.m.dong@intel.com>
Reviewed-on: https://review.coreboot.org/18038
Tested-by: build bot (Jenkins)
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
37 files changed