jbd2: fix kernel-doc notation

Fix kernel-doc notation in jbd2.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>