hwc/overlay: Add Color layer support in MDP Composition.

1. Color layer has a destination rectangle, RGBA color and plane
   alpha. There is no gralloc buffer. Layer flag "HWC_COLOR_FILL"
   denotes a Color layer.
2. There is no color member in HWC layer, so RGBA color value
   is passed via the "tranform" member from framework to HAL.

Change-Id: I8769fd3f5febcaf952a1456de0a4262679c9a0e4
diff --git a/liboverlay/pipes/overlayGenPipe.cpp b/liboverlay/pipes/overlayGenPipe.cpp
index 35f686c..2bf2369 100644
--- a/liboverlay/pipes/overlayGenPipe.cpp
+++ b/liboverlay/pipes/overlayGenPipe.cpp
@@ -93,6 +93,10 @@
     mCtrlData.ctrl.setCrop(d);
 }
 
+void GenericPipe::setColor(const uint32_t color) {
+    mCtrlData.ctrl.setColor(color);
+}
+
 void GenericPipe::setTransform(const utils::eTransform& orient) {
     mCtrlData.ctrl.setTransform(orient);
 }