ext4: fix compile error while opening the macro DOUBLE_CHECK

the error is:
    fs/ext4/mballoc.c:475:43: error: 'struct ext4_group_info' has
no member named 'bb_bitmap'.
    so, the definition of macro DOUBLE_CHECK should before
'struct ext4_group_info', I fixed it, and I moved the macro
AGGRESSIVE_CHECK together, because I think they shoule be together.
Signed-off-by: NAihua Zhang <zhangaihua1@huawei.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -41,6 +41,18 @@
  * The fourth extended filesystem constants/structures
  */
 
+/*
+ * with AGGRESSIVE_CHECK allocator runs consistency checks over
+ * structures. these checks slow things down a lot
+ */
+#define AGGRESSIVE_CHECK__
+
+/*
+ * with DOUBLE_CHECK defined mballoc creates persistent in-core
+ * bitmaps, maintains and uses them to check for double allocations
+ */
+#define DOUBLE_CHECK__
+
 /*
  * Define EXT4FS_DEBUG to produce debug messages
  */

fs/ext4/mballoc.h

@@ -22,18 +22,6 @@
 #include "ext4_jbd2.h"
 #include "ext4.h"
 
-/*
- * with AGGRESSIVE_CHECK allocator runs consistency checks over
- * structures. these checks slow things down a lot
- */
-#define AGGRESSIVE_CHECK__
-
-/*
- * with DOUBLE_CHECK defined mballoc creates persistent in-core
- * bitmaps, maintains and uses them to check for double allocations
- */
-#define DOUBLE_CHECK__
-
 /*
  */
 #ifdef CONFIG_EXT4_DEBUG