linux-phytec-fsl

Documentation: usb: gadget-testing: add description for depth of queue

Add both bulk and iso depth of queue for sourcesink.

Reviewed-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>