usb: isp1760: Prefix driver data structures with isp1760_

The slotinfo and memory_chunk structures are specific to the driver and
defined in a header file. Prefix them with isp1760_ to avoid namespace
clashes.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>