dt-bindings: usb: Convert xHCI bindings to DT schema

Currently the DT bindings of Generic xHCI Controllers are described by
means of the legacy text file. Since such format is deprecated in favor of
the DT schema, let's convert the Generic xHCI Controllers bindings file to
the corresponding yaml files. There will be two of them: a DT schema for
the xHCI controllers on a generic platform and a DT schema validating a
generic xHCI controllers properties. The later will be used to validate
the xHCI controllers, which aside from some vendor-specific features
support the basic xHCI functionality.

An xHCI-compatible DT node shall support the standard USB HCD properties
and custom ones like: usb2-lpm-disable, usb3-lpm-capable,
quirk-broken-port-ped and imod-interval-ns. In addition if a generic xHCI
controller is being validated against the DT schema it is also supposed to
be equipped with mandatory compatible string, single registers range,
single interrupts source, and is supposed to optionally contain up to two
reference clocks for the controller core and CSRs.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201210090944.16283-8-Sergey.Semin@baikalelectronics.ru


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