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, dwc2.ko is built for host,
peripheral, and dual-role mode. The PCI bus interface will be called
dwc2_pci.ko and the platform interface module will be called dwc2_platform.ko.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>