usb: dwc3-meson-g12a: skip phy on -ENODATA aswell

If the PHY isn't specified in the DT, -ENODATA means it should be skipped,
handle it like -ENOENT.

With that, devices without USB3 supported can have USB working (Odroid-HC4).

Fixes: adb049ab ("usb: dwc3: Add Meson G12A USB Glue")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>