sctp: Correct type and usage of sctp_end_cksum()

Change the type of the crc32 parameter of sctp_end_cksum()
from __be32 to __u32 to reflect that fact that it is passed
to cpu_to_le32().

There are five in-tree users of sctp_end_cksum().
The following four had warnings flagged by sparse which are
no longer present with this change.

net/netfilter/ipvs/ip_vs_proto_sctp.c:sctp_nat_csum()
net/netfilter/ipvs/ip_vs_proto_sctp.c:sctp_csum_check()
net/sctp/input.c:sctp_rcv_checksum()
net/sctp/output.c:sctp_packet_transmit()

The fifth user is net/netfilter/nf_nat_proto_sctp.c:sctp_manip_pkt().
It has been updated to pass a __u32 instead of a __be32,
the value in question was already calculated in cpu byte-order.

net/netfilter/nf_nat_proto_sctp.c:sctp_manip_pkt() has also
been updated to assign the return value of sctp_end_cksum()
directly to a variable of type __le32, matching the
type of the return value. Previously the return value
was assigned to a variable of type __be32 and then that variable
was finally assigned to another variable of type __le32.

Problems flagged by sparse.
Compile and sparse tested only.
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/sctp/checksum.h

@@ -77,7 +77,7 @@ static inline __u32 sctp_update_cksum(__u8 *buffer, __u16 length, __u32 crc32)
 	return sctp_crc32c(crc32, buffer, length);
 }
 
-static inline __le32 sctp_end_cksum(__be32 crc32)
+static inline __le32 sctp_end_cksum(__u32 crc32)
 {
 	return cpu_to_le32(~crc32);
 }

net/netfilter/nf_nat_proto_sctp.c

@@ -36,7 +36,7 @@ sctp_manip_pkt(struct sk_buff *skb,
 {
 	struct sk_buff *frag;
 	sctp_sctphdr_t *hdr;
-	__be32 crc32;
+	__u32 crc32;
 
 	if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
 		return false;
@@ -55,8 +55,7 @@ sctp_manip_pkt(struct sk_buff *skb,
 	skb_walk_frags(skb, frag)
 		crc32 = sctp_update_cksum((u8 *)frag->data, skb_headlen(frag),
 					  crc32);
-	crc32 = sctp_end_cksum(crc32);
-	hdr->checksum = crc32;
+	hdr->checksum = sctp_end_cksum(crc32);
 
 	return true;
 }