usb: gadget: Add Uevent to notify userspace

usb: gadget: Add Uevent to notify userspace

Android userspace UsbDeviceManager relies on the
uevents generated by the composition driver to
generate user notifications. This CL adds uevents
to be generated whenever USB changes its state
i.e. connected, disconnected, configured.

This CL also intercepts the setup requests from
the usb_core anb routes it to the specific
usb function if required.

Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Change-Id: Ib3d3a78255a532f7449dac286f776c2966caf8c1