usb: gadget: udc: net2280: Remove use_dma module parameter

use_dma parameter was designed to enable the dma on the chip. It was
enabled by default.

It comes from the time when the dma was not reliable. Now it has been
working ok in production.

This patch removes this parameter.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>