hwc: qbuf: Add API to unlock all

Add API to unlock all current and previous buffers.
This is essential in suspend cases.

Change-Id: I61c26db2e0e2b3e5e7f526a62a56424a8632f1d8
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index 05bb61d..00635c5 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -195,7 +195,7 @@
                 ctx->mExtDisplay->commit();
         } else {
             ctx->mOverlay->setState(ovutils::OV_CLOSED);
-            ctx->qbuf->unlockAllPrevious();
+            ctx->qbuf->unlockAll();
         }
 
         if(!ctx->overlayInUse)