dt-bindings: USB: Add bindings for new Ingenic SoCs.

Add the USB PHY bindings for the JZ4780 SoC, the X1000 SoC and
the X1830 SoC from Ingenic.

Tested-by: 周正 (Zhou Zheng) <sernia.zhou@foxmail.com>
Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Felipe Balbi <balbi@kernel.org>