ipv6: exthdrs: Replace pskb_pull() with skb_pull() in ipv6_srh_rcv().

ipv6_rthdr_rcv() pulls these data

  - Segment Routing Header : 8
  - Hdr Ext Len            : skb_transport_header(skb)[1] << 3

needed by ipv6_srh_rcv(), so pskb_pull() in ipv6_srh_rcv() never
fails and can be replaced with skb_pull().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/exthdrs.c

@@ -402,11 +402,7 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 
 			skb_postpull_rcsum(skb, skb_network_header(skb),
 					   skb_network_header_len(skb));
-
-			if (!pskb_pull(skb, offset)) {
-				kfree_skb(skb);
-				return -1;
-			}
+			skb_pull(skb, offset);
 			skb_postpull_rcsum(skb, skb_transport_header(skb),
 					   offset);