Fix VS build break

Change-Id: I2cd4a8c96632464c3421902495c312178fa810a4
diff --git a/av1/common/cdef_block.c b/av1/common/cdef_block.c
index 5953818..76d65ad 100644
--- a/av1/common/cdef_block.c
+++ b/av1/common/cdef_block.c
@@ -199,7 +199,7 @@
       for (int iy = 0; iy < 1 << bh_log2; iy++) {
         memcpy(&dst16[(bi << (bw_log2 + bh_log2)) + (iy << bw_log2)],
                &in[((by << bh_log2) + iy) * CDEF_BSTRIDE + (bx << bw_log2)],
-               (1 << bw_log2) * sizeof(*dst16));
+               ((size_t)1 << bw_log2) * sizeof(*dst16));
       }
     }
     return;