ocfs2: move ip_created_trans to struct ocfs2_caching_info

Similar ip_last_trans, ip_created_trans tracks the creation of a journal
managed inode.  This specifically tracks what transaction created the
inode.  This is so the code can know if the inode has ever been written
to disk.

This behavior is desirable for any journal managed object.  We move it
to struct ocfs2_caching_info as ci_created_trans so that any object
using ocfs2_caching_info can rely on this behavior.

Signed-off-by: Joel Becker <joel.becker@oracle.com>