Display and wfd synchronization during teardown

* Provide a binder interface call for wfd module
to inform display about the start/stop/pause/resume
of wfd session.

* This is needed for wfd-hdmi synchronization in
case of v4l2 wfd solution. If hdmi is plugged
in during v4l2 wfd session, display-hal waits in
uevent thread for wfd teardown notification from
wfd module, before going ahead with configuring
external display.

* For VDS WFD solution, display-hal waits in uevent
thread for wfd-teardown to be signalled from
the composition thread.

Change-Id: I9514cb5bc7ff81de0b5dd4cdf66d8286a64ba094