usb: cdns3: gadget: add CHAIN and ISP bit for sg list use case

For sg buffer list use case, we need to add ISP for each TRB, and
add CHAIN bit for each TRB except for the last TRB.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>