usb: dwc2: add support for Meson8b and GXBB SoCs

Add compatible strings for amlogic Meson8b and GXBB SoCs with the
corresponding configuration parameters.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>