usb: gadget: Add bcdDevice for the DWC2 USB Gadget Controller

Add an entry in usb_gadget_controller_number() for the DWC2
gadget controller. It is used to bind the USB Ethernet driver.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reported-by: Herbert Poetzl <herbert@13thfloor.at>
Cc: Marek Vasut <marex@denx.de>
Cc: Herbert Poetzl <herbert@13thfloor.at>