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

vp8/encoder/psnr.c

diff --git a/vp8/encoder/psnr.c b/vp8/encoder/psnr.c
index 5bb49ad..b3a3d95 100644
--- a/vp8/encoder/psnr.c
+++ b/vp8/encoder/psnr.c
@@ -13,7 +13,7 @@
 #include "math.h"
 #include "vp8/common/systemdependent.h" /* for vp8_clear_system_state() */
 
-#define MAX_PSNR 60
+#define MAX_PSNR 100
 
 double vp8_mse2psnr(double Samples, double Peak, double Mse)
 {