x86: Fix up byteorder.h for x86_64

Remove the very old x86 code and add support for 64-bit.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Merge branch 'master' of git://git.denx.de/u-boot-x86

x86: Rename i386 to x86

Signed-off-by: Graeme Russ <graeme.russ@gmail.com>