overlay: writeback: Add dumpsys info

Add dumpsys information from writeback data structure.
Remove some unused fields, formatting to save space.

Change-Id: I808ce67aae16e27c3aa6d6db45983929b1386b69
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index 5038025..2c255e1 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -770,6 +770,9 @@
     ovDump[0] = '\0';
     ctx->mRotMgr->getDump(ovDump, 1024);
     dumpsys_log(aBuf, ovDump);
+    ovDump[0] = '\0';
+    Writeback::getInstance()->getDump(ovDump, 1024);
+    dumpsys_log(aBuf, ovDump);
     strlcpy(buff, aBuf.string(), buff_len);
 }