Partial revert "Remove mapper from composer2.1 VTS"

This reverts commit 6d0abbb439a8eb7199beeae35e599d6594edbbef.

The original change causes some graphics composers to trigger overflow
exceptions when adding displays.

Change-Id: I143f7361bdf5f3e7e1e788a47b1ee1158a06fe04
3 files changed