ANDROID: usb: gadget: configfs: 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.

Bug: 68755607
Bug: 120441124
Change-Id: Ib3d3a78255a532f7449dac286f776c2966caf8c1
[badhri: Migrate to using udc uevents from upstream sysfs.]
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
[AmitP: Folded following android-4.9 commit changes into this patch
        9214c899f730 ("ANDROID: usb: gadget: configfs: handle gadget reset request for android")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
[astrachan: Folded change 5c899c9fd75d ("ANDROID: usb: gadget: configfs:
            fix null ptr in android_disconnect") into this patch]
Signed-off-by: Alistair Strachan <astrachan@google.com>