[DCCP]: Combine allocating & zeroing header space on skb

This is a code simplification:
it combines three often recurring operations into one inline function,

        * allocate `len' bytes header space in skb
        * fill these `len' bytes with zeroes
        * cast the start of this header space as dccp_hdr

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 6f1c2ad..116bddb 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -537,9 +537,7 @@
 
 	skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_reset_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_reset_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 
 	/* Swap the send and the receive. */
 	dh->dccph_type	= DCCP_PKT_RESET;
@@ -601,9 +599,7 @@
 
 	skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_ack_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_ack_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_ack_len);
 
 	/* Build DCCP header and checksum it. */
 	dh->dccph_type	= DCCP_PKT_ACK;