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: Aihua Zhang <[e-mail]>
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext4/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__
+
+/*
  * Define EXT4FS_DEBUG to produce debug messages
  */
 #undef EXT4FS_DEBUG

fs/ext4/mballoc.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
 extern ushort ext4_mballoc_debug;