Some resources, such as IPPC register etc, shared with device
driver are moved into common glue layer when xHCI driver is the
host side of dual-role mode and they should be changed as optional
properties if they are required ones before. For clarity, add
a new part of binding to support host side of dual-role mode.

Additionally add optional properties of pinctrl for host only mode
Signed-off-by: NChunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>