flashchips: Add Spansion 25FL256S......0

The Spansion 25SFL256S supports 4BA through an extended address register,
a 4BA mode set by bit 7 of that register, or native 4BA instructions.
Enable the former only for now.

Unfortunately the S25SF256S uses another instruction to write the exten-
ded address register. So we add an override for the instruction byte.

Change-Id: I0a95a81dfe86434f049215ebd8477392391b9efc
Signed-off-by: Nico Huber <nico.h@gmx.de>
Tested-by: Michael Fuckner <michael@fuckner.net>
Reviewed-on: https://review.coreboot.org/25132
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
3 files changed