usb: gadget: dwc2_udc_otg: set ep's desc during enable/disable

Fastboot support has been broken on platforms using dwc2 controller
since the gadget gets its max packet size from it.
This patch is the equivalent of 723fd566 which fixed the same issue
but for the chipidea controller.

Fixes: 27c9141b ("usb: gadget: fastboot: use correct max packet size")

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>