ocfs2: use ocfs2_alloc_dinode_update_counts() instead of open coding

ocfs2_search_chain() makes the same updates as
ocfs2_alloc_dinode_update_counts to the alloc inode. Instead of open coding
the bitmap update, use our helper function.

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Tao Ma <tao.ma@oracle.com>