cpu/intel/model_2065x: Switch to POSTCAR_STAGE

Also removes some non-POSTCAR_STAGE functions, since those are unused
now.

Change-Id: I439bffbe39411186355d374eed7d5efd63fb02e3
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/26792
Reviewed-by: Matthias Gazzari <mail@qtux.eu>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
5 files changed