usb: dwc3: pci: Register a software node for the dwc3 platform device

By registering the software node directly instead of just
the properties in it, the driver can take advantage of also
the other features the software nodes have.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20210115094914.88401-3-heikki.krogerus@linux.intel.com


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