drivers: usb: udc_dwc2: Support Remote Wakeup

According to USB 2.0 Specification the remote wakeup device must hold
the resume signaling for at least 1 ms but for no more than 15 ms. The
DWC2 otg controller requires the software to drive the remote wakeup
signalling for appropriate duration (when LPM is disabled, which is
currently always the case in udc_dwc2). Arbitrarily choose to drive the
resume signalling for 2 ms to have sufficient margin in both directions.

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>