hwc: Check vsync state before sending it up

The vsync enable ioctl is called in  a separate thread in a
recent change
Hence it was now possible that vsync could be disabled but
SurfaceFlinger still received a vsync. With this check we make
sure that doesn't happen.

Change-Id: I459c0b98ab9ce972d86a361c5ecdfe0c1a2d0e74
diff --git a/libhwcomposer/hwc_vsync.cpp b/libhwcomposer/hwc_vsync.cpp
index 559cd7d..b42043f 100644
--- a/libhwcomposer/hwc_vsync.cpp
+++ b/libhwcomposer/hwc_vsync.cpp
@@ -136,9 +136,11 @@
             cur_timestamp = systemTime();
         }
         // send timestamp to HAL
-        ALOGD_IF (logvsync, "%s: timestamp %llu sent to HWC for %s",
-                  __FUNCTION__, cur_timestamp, "fb0");
-        ctx->proc->vsync(ctx->proc, dpy, cur_timestamp);
+        if(ctx->vstate.enable) {
+            ALOGD_IF (logvsync, "%s: timestamp %llu sent to HWC for %s",
+                      __FUNCTION__, cur_timestamp, "fb0");
+            ctx->proc->vsync(ctx->proc, dpy, cur_timestamp);
+        }
 
     } while (true);
     if(fd_timestamp >= 0)