mainboard/gizmosphere/gizmo2: Start adding new mainboard

This is a direct copy of the amd/olivehill mainboard which
will be the starting point for this port.

Change-Id: I6a643f7ac35d89e21df0ffdf4e61a2da46e19b82
Signed-off-by: Dave Frodin <dave.frodin@se-eng.com>
Reviewed-on: http://review.coreboot.org/7721
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)