intel post-car: Consolidate choose_top_of_stack()

Change-Id: I2c49d68ea9a8f52737b6064bc4fa703bdb1af1df
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/15463
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
8 files changed