openswitch: fix typo CONFIG_NF_CONNTRACK_LABEL

Fix typo in conntrack.c
s/CONFIG_NF_CONNTRACK_LABEL/CONFIG_NF_CONNTRACK_LABELS/

Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>