ARM: dts: msm: Add device node for Venus on msmcobalt

Add a device node minimally describing Venus capabilities on msmcobalt.
The device status is also marked as "disabled" as the driver isn't fully
functional yet.

Change-Id: I8b0f03012adde31ffceec2598a34e84b4e387a52
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>