[IPV4]: Remove dead code from ip_output.c

skb_prev is assigned from skb, which cannot be NULL. This patch removes the
unnecessary NULL check.

Signed-off-by: Jayachandran C. <c.jayachandran at gmail.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

net/ipv4/ip_output.c

@@ -1023,10 +1023,7 @@ ssize_t	ip_append_page(struct sock *sk, struct page *page,
 			int alloclen;
 
 			skb_prev = skb;
-			if (skb_prev)
 			fraggap = skb_prev->len - maxfraglen;
-			else
-				fraggap = 0;
 
 			alloclen = fragheaderlen + hh_len + fraggap + 15;
 			skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);