arm/dt: msm8974: Add Wifi Display device to the device tree

Add the Wifi Display device for msm8974.  The Wifi Display device
captures frames from the MDP, encodes them, and provides the encoded
frames to the userspace client for transmission.

Change-Id: I91efa575b9008b4141f76450571013ad2949a350
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>
Signed-off-by: Arun Menon <menon@codeaurora.org>