dt-bindings: phy: imx8mq-usb-phy: convert to json schema

Convert to jason schema.

Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Li Jun <jun.li@nxp.com>
Cc: linux-phy@lists.infradead.org
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210715082536.1882077-5-aisheng.dong@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>