hwc/overlay: Add support for pipe priorities, 1 pipe config for FB

If using source split to stage 2 pipes on the same mixer stage,
the left pipe needs to be a higher priority than the right.

Add API in overlay to compare pipe priorities and use this in
source split config to stage pipes accordingly.

Add support for 1 pipe config for FB if updating rect is within 2048
pixels.

Change-Id: I8b33d5ebd0f8765ee842bab128d8abd67a110145
diff --git a/liboverlay/overlayMdp.h b/liboverlay/overlayMdp.h
index 843556b..d312c2e 100644
--- a/liboverlay/overlayMdp.h
+++ b/liboverlay/overlayMdp.h
@@ -80,6 +80,8 @@
     utils::Dim getDstRectDim() const;
     /* returns a copy to src rect dim */
     utils::Dim getSrcRectDim() const;
+    /* return pipe priority */
+    uint8_t getPriority() const;
     /* setVisualParam */
     bool setVisualParams(const MetaData_t& data);
 
@@ -304,6 +306,10 @@
         mOVInfo.flags |= MDP_SOURCE_ROTATED_90;
 }
 
+inline uint8_t MdpCtrl::getPriority() const {
+    return mOVInfo.priority;
+}
+
 ///////    MdpCtrl3D //////
 
 inline MdpCtrl3D::MdpCtrl3D() { reset(); }