SF: Round the min/max checking to the closest int

Pixel display config is reporting FPS for a given display at 60.000004.
Make sure to take a small deviation into the account.

Test: manual. open swappy and change between refresh rates.
Test: manual. open setting and turn smooth display on/off.
Test: unit.
Change-Id: I0086c98406a2bd1a9b836fa171b8be14f3152acd
Bug: 147252378