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>
diff --git a/hwaccess_physmap.c b/hwaccess_physmap.c
index 5644680..1088405 100644
--- a/hwaccess_physmap.c
+++ b/hwaccess_physmap.c
@@ -24,7 +24,7 @@
 #include <string.h>
 #include <errno.h>
 #include "flash.h"
-#include "hwaccess.h"
+#include "platform.h"
 #include "hwaccess_physmap.h"
 
 #if !defined(__DJGPP__) && !defined(__LIBPAYLOAD__)