ARM: dts: msm: Add VFE parent node for 8996

Create parent layer for vfe0 and vfe1. This enables the parent node
driver to control child HW and also helps to sync between the child HW.

Change-Id: Ia3d723ff40a29508c98146af159bf1bc60805b95
Signed-off-by: Harsh Shah <harshs@codeaurora.org>
Signed-off-by: Peter Liu <pingchie@codeaurora.org>