board: usb: Replace legacy usb_gadget_handle_interrupts()

The usb_gadget_handle_interrupts() is no longer used anywhere,
replace the remaining uses with dm_usb_gadget_handle_interrupts()
which takes udevice as a parameter.

Some of the UDC drivers currently ignore the index parameter altogether,
those also ignore the udevice and have to be reworked. Other like the
dwc3_uboot_handle_interrupt() had to be switched from index to udevice
look up to avoid breakage.

Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # on khadas vim3
Signed-off-by: Marek Vasut <marex@denx.de>