Plumb getClientTargetProperty API.

getClientTargetProperty will give hardware composer the ability to request some
properties of the client target that hardware composer wants. Prior to this
API, the client will does its best to produce the client target of which the
properties are pretty much fixed.

This patch implements the parsing of SET_CLIENT_TARGET_PROPERTY command in
order to get the client target property from hardware composer.

BUG: b/145968912
Test: m -j32
Change-Id: I3e738b2617e4472c7876aa283c0964e2240b144b