ocfs2: Remove ocfs2_sync_inode()

ocfs2_sync_inode() is used only from ocfs2_sync_file(). But all data has
already been written before calling ocfs2_sync_file() and ocfs2 doesn't use
inode's private_list for tracking metadata buffers thus sync_mapping_buffers()
is superfluous as well.

Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>