dt-bindings: usb: mtk-xhci: update USB wakeup properties

Add two arguments in "mediatek,syscon-wakeup" to support multi
wakeup glue layer between SSUSB and SPM, and use standard property
"wakeup-source" to replace the private "mediatek,wakeup-src"

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>