hwc/overlay: Fix dma mode design and issues.

Add support for tracking the mode in which DMA is being used in overlay.
Remove unnecessary tracking variables, and their set,reset inconsistency.

With such varibles in hwc, it still leads to overlay giving out DMA pipes.
Make overlay as the single tracking place.

Change-Id: Ib949f3d0ef5918ef323c81cb1768b68a68c83da4
diff --git a/liboverlay/overlay.h b/liboverlay/overlay.h
index fdeebc2..0cedac9 100644
--- a/liboverlay/overlay.h
+++ b/liboverlay/overlay.h
@@ -40,6 +40,8 @@
 
 class Overlay : utils::NoCopy {
 public:
+    enum { DMA_BLOCK_MODE, DMA_LINE_MODE };
+
     /* dtor close */
     ~Overlay();
 
@@ -84,6 +86,8 @@
      * to populate.
      */
     void getDump(char *buf, size_t len);
+    static void setDMAMode(const int& mode);
+    static int getDMAMode();
 
 private:
     /* Ctor setup */
@@ -148,6 +152,7 @@
     /* Singleton Instance*/
     static Overlay *sInstance;
     static int sExtFbIndex;
+    static int sDMAMode;
 };
 
 inline void Overlay::validate(int index) {
@@ -176,6 +181,15 @@
     return sExtFbIndex;
 }
 
+inline void Overlay::setDMAMode(const int& mode) {
+    if(mode == DMA_LINE_MODE || mode == DMA_BLOCK_MODE)
+        sDMAMode = mode;
+}
+
+inline int Overlay::getDMAMode() {
+    return sDMAMode;
+}
+
 inline bool Overlay::PipeBook::valid() {
     return (mPipe != NULL);
 }