netfilter: nf_conntrack_sctp: fix sparse warnings

Introduced by a258860e (netfilter: ctnetlink: add full support for SCTP to ctnetlink):

net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: incorrect type in argument 1 (different base types)
net/netfilter/nf_conntrack_proto_sctp.c:483:2:    expected unsigned int [unsigned] [usertype] x
net/netfilter/nf_conntrack_proto_sctp.c:483:2:    got restricted unsigned int const <noident>
net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:483:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: incorrect type in argument 1 (different base types)
net/netfilter/nf_conntrack_proto_sctp.c:487:2:    expected unsigned int [unsigned] [usertype] x
net/netfilter/nf_conntrack_proto_sctp.c:487:2:    got restricted unsigned int const <noident>
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:487:2: warning: cast from restricted type
net/netfilter/nf_conntrack_proto_sctp.c:532:42: warning: incorrect type in assignment (different base types)
net/netfilter/nf_conntrack_proto_sctp.c:532:42:    expected restricted unsigned int <noident>
net/netfilter/nf_conntrack_proto_sctp.c:532:42:    got unsigned int
net/netfilter/nf_conntrack_proto_sctp.c:534:39: warning: incorrect type in assignment (different base types)
net/netfilter/nf_conntrack_proto_sctp.c:534:39:    expected restricted unsigned int <noident>
net/netfilter/nf_conntrack_proto_sctp.c:534:39:    got unsigned int

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>