gralloc: Deprecate old stuff.

1. Reclaim some old gralloc flags.
2. System heap allocation happens by default.
3. Remove some unused private flags.
4. Add heapid member to alloc_data to better line up with ion
   header
5. Remove check for MDSS_TARGET

Change-Id: I37be0a2fcd5fd4a14bb9ca235fcae41f6f3ec19e
diff --git a/libgralloc/memalloc.h b/libgralloc/memalloc.h
index 2bc1ddf..598d983 100644
--- a/libgralloc/memalloc.h
+++ b/libgralloc/memalloc.h
@@ -49,6 +49,7 @@
     uintptr_t      pHandle;
     bool           uncached;
     unsigned int   flags;
+    unsigned int   heapId;
     int            allocType;
 };