Fix a logspam

On skiavk the flush to GPU happens sooner than it does on skiagl,
which was resulting in false-positive warning logs. Adjust the
condition to avoid this, so it should now only log if the GPU
fence time is significantly incorrect.

Fixes: 180488606
Test: doesn't log on skiavk
Change-Id: Ie6546b788663b5d863fb064f55245bead4eb0160