MLK-22357-1 usb: Add handle_interrupts function pointer for UCLASS_USB_GADGET_GENERIC

MLK-22357-1 usb: Add handle_interrupts function pointer for UCLASS_USB_GADGET_GENERIC

Since the orginal way to call interrupts handle function of DM usb
gadget driver is through dm_usb_gadget_handle_interrupts(), when we want
to use two or more different gadget drivers at the same time, it will
cause error of duplicate names.

So here add a handle_interrupts function pointer instead of driectly
call dm_usb_gadget_handle_interrupts(), then the error can be avoided.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>