graphics: add a default implementation to IMapper

The default implementatoin is built on top of conventional gralloc1.

Test: make android.hardware.graphics.mapper.hallib
Change-Id: I8647dc69dbb1637a141d36358d5769f450422ac1
diff --git a/Android.bp b/Android.bp
index f281faf..aed6b47 100644
--- a/Android.bp
+++ b/Android.bp
@@ -6,6 +6,7 @@
     "graphics/allocator/2.0",
     "graphics/allocator/2.0/default",
     "graphics/mapper/2.0",
+    "graphics/mapper/2.0/default",
     "memtrack/1.0",
     "memtrack/1.0/default",
     "nfc/1.0",