openvswitch: Fix an error handling path in 'ovs_nla_init_match_and_action()'

All other error handling paths in this function go through the 'error'
label. This one should do the same.

Fixes: 9cc9a5cb ("datapath: Avoid using stack larger than 1024.")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>