usb: dwc2: Update Kconfig to support dual-role

Update DWC2 kconfig and makefile to support dual-role mode. The platform
file will always get compiled for the case where the controller is directly
connected to the CPU. So for loadable modules, only dwc2.ko is needed.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>