usb: dwc3: Registering a role switch in the DRD code.

The Type-C drivers use USB role switch API to inform the
system about the negotiated data role, so registering a role
switch in the DRD code in order to support platforms with
USB Type-C connectors.

Cc: John Stultz <john.stultz@linaro.org>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Yu Chen <chenyu56@huawei.com>