test_extended_copy_simple: Fix buffer comparison code

Compare the buffers in their entirety instead of only a prefix of
the buffers.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>

test-tool/test_extendedcopy_simple.c

@@ -75,7 +75,7 @@ test_extendedcopy_simple(void)
                block_size, 0, 0, 0, 0, 0, buf2,
                EXPECT_STATUS_GOOD);
 
-        if (memcmp(buf1, buf2, 2048)) {
+        if (memcmp(buf1, buf2, 2048*block_size)) {
                 CU_FAIL("Blocks were not copied correctly");
         }