netfilter: nf_ct_dccp: add missing DCCP protocol changes in event cache

This patch adds the missing protocol state-change event reporting
for DCCP.

$ sudo conntrack -E
    [NEW] dccp     33 240 src=192.168.0.2 dst=192.168.1.2 sport=57040 dport=5001 [UNREPLIED] src=192.168.1.2 dst=192.168.1.100 sport=5001 dport=57040

With this patch:

$ sudo conntrack -E
    [NEW] dccp     33 240 REQUEST src=192.168.0.2 dst=192.168.1.2 sport=57040 dport=5001 [UNREPLIED] src=192.168.1.2 dst=192.168.1.100 sport=5001 dport=57040

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>