HACK: usb: gadget: fix android composite driver build

Even though Android is moving away from usb compsite gadget
driver to  ConfigFS gadgets, plan is to provide backward
compatibility to some extent.

This patch is a set of build fixes we're using at Linaro for
broken Android composite driver. I suspect much of this is
incorrect, but wanted to submit it as a starting place to
get things fixed and hopefully be able to get atleast ADB
working with this legacy Android composite gadget driver.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>