overlay: Add support for pipe dumps.

Add support for pipe state dump useful in dumpsys.
Reduce debug log spam when mdp state changes.

Change-Id: Ie27ad00698085e2ffd6166ad2f7503fe16a571f8
diff --git a/liboverlay/overlayMdp.h b/liboverlay/overlayMdp.h
index c1684fc..55e2787 100644
--- a/liboverlay/overlayMdp.h
+++ b/liboverlay/overlayMdp.h
@@ -141,9 +141,6 @@
     /* using user_data, sets/unsets roationvalue in mdp flags */
     void setRotationFlags();
 
-    /* dump state of the object */
-    void dump() const;
-
     /* Perform transformation calculations */
     void doTransform();
 
@@ -156,6 +153,12 @@
     /* Update the src format */
     void updateSrcformat(const uint32_t& inputsrcFormat);
 
+    /* dump state of the object */
+    void dump() const;
+
+    /* Return the dump in the specified buffer */
+    void getDump(char *buf, size_t len);
+
 private:
 
     /* helper functions for overlayTransform */
@@ -237,6 +240,10 @@
 
     /* dump state of the object */
     void dump() const;
+
+    /* Return the dump in the specified buffer */
+    void getDump(char *buf, size_t len);
+
 private:
 
     /* actual overlay mdp data */