Btrfs: fix overlap of fs_info::flags values

Because the values of BTRFS_FS_EXCL_OP and BTRFS_FS_QUOTA_OVERRIDE overlap,
we should change the value.

First, BTRFS_FS_EXCL_OP was set to 14.

  commit 171938e5 ("btrfs: track exclusive filesystem operation in flags")

Next, the value of BTRFS_FS_QUOTA_OVERRIDE was set to 14.

  commit f29efe29 ("btrfs: add quota override flag to enable quota override for CAP_SYS_RESOURCE")

As a result, the value 14 overlapped, by accident.
This problem is solved by defining the value of BTRFS_FS_EXCL_OP as 16,
the flags are internal.

Fixes: f29efe29 ("btrfs: add quota override flag to enable quota override for CAP_SYS_RESOURCE")
CC: stable@vger.kernel.org # 4.13+
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minimize the change, update only BTRFS_FS_EXCL_OP ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -721,7 +721,7 @@ struct btrfs_delayed_root;
  * Indicate that a whole-filesystem exclusive operation is running
  * (device replace, resize, device add/delete, balance)
  */
-#define BTRFS_FS_EXCL_OP			14
+#define BTRFS_FS_EXCL_OP			16
 
 struct btrfs_fs_info {
 	u8 fsid[BTRFS_FSID_SIZE];