Changed MAX_PSNR to 100

The MAX_PSNR was used to assign a "psnr" number when the mse is close
to zero. The direct assignment is used to prevent divide by zero in
computation. Changing it from 60 to 100 to be consistent against what
is being done in VP9

Change-Id: I4854ffc4961e59d372ec8005a0d52ca46e3c4c1a
1 file changed