msm: camera2: port VPE module to pproc framework

To better support Android Camera 2.0, the postprocessing component was
rewritten to be a generic module with sink ports and source ports to
communicate with other modules. An imaging pipeline can be formed by
linking some modules together. In the new framework, v4l2 subdevices
don't communicate with each other in the kernel. Instead, user space
code accesses different subdevice nodes, and coordinate among
themselves. This change ports the VPE driver into this new framework.

Change-Id: I913fc5cc9342d53e2aa8680868d3ca7c079b6f35
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>