tiny_psnr: fix range calculation for sample size of 32 bits

For a sample size of 32 bits, the shift would overflow producing
undefined results.  Incidentally, in the only test currently using
32-bit samples, the output matches the reference exactly on most
systems meaning the bad 'max' value is never used.
Signed-off-by: Mans Rullgard <mans@mansr.com>

tests/tiny_psnr.c

@@ -146,7 +146,7 @@ int main(int argc, char *argv[])
         }
     }
 
-    max = (1 << (8 * len)) - 1;
+    max = (1LL << (8 * len)) - 1;
 
     f[0] = fopen(argv[1], "rb");
     f[1] = fopen(argv[2], "rb");