usb: gadget: f_rndis: OS descriptors support

In order for usb functions to expose OS descriptors they
need to be made aware of OS descriptors. This involves
extending the "options" structure and setting up
appropriate associations.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>