Fix possible infinite loop decoding als.

Reviewed-by: Thilo Borgmann
(cherry picked from commit f0f2babca2)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/alsdec.c

@@ -1012,7 +1012,7 @@ static void zero_remaining(unsigned int b, unsigned int b_max,
     unsigned int count = 0;
 
     while (b < b_max)
-        count += div_blocks[b];
+        count += div_blocks[b++];
 
     if (count)
         memset(buf, 0, sizeof(*buf) * count);