ocfs2: fix build for OCFS2_FS_STATS not enabled

When CONFIG_OCFS2_FS_STATS is not enabled:

fs/ocfs2/cluster/tcp.c:1254: error: implicit declaration of function 'o2net_update_recv_stats'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc:	Mark Fasheh <mfasheh@suse.com>
Cc:	Joel Becker <joel.becker@oracle.com>
Cc:	ocfs2-devel@oss.oracle.com
Signed-off-by: Joel Becker <joel.becker@oracle.com>