dt-bindings: usb: snps,dwc3: Split core description

The Synopsys DWC3 core is found either as a standalone block or
integrated with vendor glue logic. So far the latter has been described
as two separate IP blocks in DeviceTree, but the two parts are not
separate.

In the case where the core is integrated together with vendor glue,
resources such as clock and resets are often customized by the vendor,
such that the standard properties doesn't make sense.

Split the snps,dwc3 binding in a description of the core properties and
the standard "glue" properties, in order to allow vendor bindings to
inherit the core properties.

Reviewed-by: Rob Herring (Arm) <[email protected]>
Signed-off-by: Bjorn Andersson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: quic-bjorande