tests/kms_flip: Improve the accuracy of out frame time calculation
tests/kms_flip: Improve the accuracy of out frame time calculation

Don't use the rounded vrefresh info to predict the frame duration.
Instead calculate if from the clock.

Signed-off-by: Ville Syrjälä <cd6e8d405ca90be3a03d5427c5b24fbd2d68dcc4@linux.intel.com>

chenxianqin/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools