usb: gadget: udc: atmel: Fix interrupt storm in FIFO mode.

Fix interrupt storm generated by endpoints when working in FIFO mode.
The TX_COMPLETE interrupt is used only by control endpoints processing.
Do not enable it for other types of endpoints.

Fixes: 914a3f3b

 ("USB: add atmel_usba_udc driver")
Signed-off-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>