usb: dwc3: add generic driver to support flattened

To support flattened dwc3 dt model and drop the glue layer, introduce the
`dwc3-generic` driver. This enables direct binding of the DWC3 core driver
and offers an alternative to the existing glue driver `dwc3-of-simple`.

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Ze Huang <huang.ze@linux.dev>
Link: https://lore.kernel.org/r/20250913-dwc3_generic-v8-2-b50f81f05f95@linux.dev


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250913-dwc3_generic-v8-2-b50f81f05f95@linux.dev