hwc: Add vpu client

Stub implementation of VPU in HWC.
This commit passes through binder calls from HWC
to the VPU library. It also has stub prepare/draw calls
in the VPU client object which can be used to configure
VPU in the composition cycle.

Change-Id: I2606f2884e870448d29ef26e02faac92e157e2c6
13 files changed