Temp fix for overdimming issue in silkFX.

- disable caching if hdr/sdr ratio > 1.01f, which we uses the extended
  brightness api.

Bug: 273624686
Test: play HDR video in silkFX and make sure no overdimming obeserved;
atest libcompositionengine_test

Change-Id: Iae53c5928e4f91b4b73f9e4ee9dd7bb052e86090