SurfaceFlinger: use margin when comparing fps in PhaseOffsets

To avoid any incorrect float equality due to precision errors
use 0.01Hz margin.

Test: adb shell /data/nativetest64/libsurfaceflinger_unittest/libsurfaceflinger_unittest
Bug: 147358911
Change-Id: Ief43eb7b5064b250a6255fd41542640d9c77529d
2 files changed