usb: gadget: sandbox: Drop dm_usb_gadget_handle_interrupts()

usb: gadget: sandbox: Drop dm_usb_gadget_handle_interrupts()

Drop dm_usb_gadget_handle_interrupts() in favor of empty default
implementation of the same in drivers/usb/gadget/udc/udc-uclass.c .

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # vim3
Link: https://lore.kernel.org/r/20240614005309.34433-11-marek.vasut+renesas@mailbox.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>