drivers: usb_dc_stm32: implement usb_dc_wakeup_request

Implement usb_dc_wakeup_request for STM32 USB DC and default to enable
remote wakeup functionality when the drivers is selected.

This allows the device to wake the host up by calling
usb_wakeup_request().

Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>