drm/msm/sde: add hardware driver support for chroma down module

Chroma down module is used to perform color space conversion and
downsampling of luma/chroma components.  This patch adds support
for chroma down hardware driver to control the hardware block using
hardware abstraction api common across families of hardware.

Change-Id: Ic7f420572d06b312aafbba19832d053a9e1a4aea
Signed-off-by: Alan Kwong <akwong@codeaurora.org>