devicetree: bindings: phy: Document ipq806x dwc3 qcom phy

Document dwc3 qcom phy hs and ss phy bindings needed to correctly
inizialize and use usb on ipq806x SoC.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200717131635.11076-2-ansuelsmth@gmail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>