Endian conversion: move to platform.h and platform/endian*.c

Starting to move the platform dependent code to platform/ and provide
the abstraction through the platform.h header.

Change-Id: I35640282d451960f2a329ae24339ec05dbae6d30
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/62899
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72316
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
6 files changed