usb: dwc2: Allow for enabling USB if the cable is disconnected

Adds CONFIG_UDC_DWC2_USBHS_VBUS_READY_TIMEOUT_MS that allows
for waiting for a USBHS VBUS ready event for a specified
amount of time. Earlier it waited forever and because of that,
the udc_enable() was blocked forever if the USB cable was
disconnected. Now the function returns error on timeout.

Signed-off-by: Aleksander Strzebonski <aleksander.strzebonski@nordicsemi.no>