dt-bindings: usb: Convert DWC USB3 bindings to DT schema

DWC USB3 DT node is supposed to be compliant with the Generic xHCI
Controller schema, but with additional vendor-specific properties, the
controller-specific reference clocks and PHYs. So let's convert the
currently available legacy text-based DWC USB3 bindings to the DT schema
and make sure the DWC USB3 nodes are also validated against the
usb-xhci.yaml schema.

Note 1. we have to discard the nodename restriction of being prefixed with
"dwc3@" string, since in accordance with the usb-hcd.yaml schema USB nodes
are supposed to be named as "^usb(@.*)".

Note 2. The clock-related properties are marked as optional to match the
DWC USB3 driver expectation and to improve the bindings mainainability
so in case if there is a glue-node it would the responsible for the
clocks initialization.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201210090944.16283-11-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>