dm: usb: udc: Drop legacy udevice handler functions

Remove legacy functions limited by the dev_array array,
those are no longer used anywhere, all the code uses
plain udevice based access now.

The usb_gadget_handle_interrupts() is doing udevice look up
until all call sites use dm_usb_gadget_handle_interrupts().

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