SurfaceFlinger: Enable ealy offset for reused client composition

In the condition of reused client composition, SurfaceFlinger still
needed to call 'validate' and 'presentDisplay' and resulted in longer
execution time. Before we can enable skip validation in this case, we
need to provide the early offset to fit HWC behavior.

Bug: 160552879
Test: Check the Vsync offset in PIP
Change-Id: I6d11c6b1409997f550cf2441bba67de08ffb25a8