Switch DTB provider form OF_EMBED to OF_SEPARATE
to avoid the compile warning message:
==================== WARNING ======================
CONFIG_OF_EMBED is enabled. This option should only
be used for debugging purposes. Please use
CONFIG_OF_SEPARATE for boards in mainline.
See doc/README.fdt-control for more info.
====================================================
Signed-off-by: Chia-Wei, Wang <chiawei_wang@aspeedtech.com>