AGESA f12: Add "const" modifiers

Apply commit 283ba78415 to f12 (literally, plus one adaptation).

Change-Id: Ied7891806e269320caf968cae3de3dc792c5f8fd
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: http://review.coreboot.org/7312
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>
AMD boards: constify romstage variables

That takes them out of .data

Change-Id: Idf88ddaacb2f78ba6a0260e3511b34edc269731d
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/7313
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>