DisplayViewport should only have actual viewports (1/2)

If input device is external, TouchInputMapper would be associated with
external display. But if external viewport is not present,
it should fallback to the internal viewport.

Bug: 116850516
Test: atest inputflinger_tests
Change-Id: I044a5c66fd28ae1d032e56791478c4c46f13ef25
2 files changed