ocfs2: ocfs2_link() journal credits update

Commit 592282cf

 fixed some missing directory
c/mtime updates in part by introducing a dinode update in ocfs2_add_entry().
Unfortunately, ocfs2_link() (which didn't update the directory inode before)
is now missing a single journal credit. Fix this by doubling the number of
inode updates expected during hard link creation.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>