Extend superblock size fo 128x128 pixels.

If --enable-ext-partition is used at build time, the superblock size
(sometimes also referred to as coding unit (CU) size) is extended to
128x128 pixels.

Change-Id: Ie09cec6b7e8d765b7555ff5d80974aab60803f3a
diff --git a/test/convolve_test.cc b/test/convolve_test.cc
index 0e54c40..fdea61f 100644
--- a/test/convolve_test.cc
+++ b/test/convolve_test.cc
@@ -28,7 +28,7 @@
 
 namespace {
 
-static const unsigned int kMaxDimension = MAX_CU_SIZE;
+static const unsigned int kMaxDimension = MAX_SB_SIZE;
 
 typedef void (*ConvolveFunc)(const uint8_t *src, ptrdiff_t src_stride,
                              uint8_t *dst, ptrdiff_t dst_stride,