dt-bindings: mediatek: Add smi dts binding

This patch add smi binding document and smi local arbiter header file.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>