net/tls: remove redundant second null check on sgout

A duplicated null check on sgout is redundant as it is known to be
already true because of the identical earlier check. Remove it.
Detected by cppcheck:

net/tls/tls_sw.c:696: (warning) Identical inner 'if' condition is always
true.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tls/tls_sw.c

@@ -693,7 +693,6 @@ static int decrypt_skb(struct sock *sk, struct sk_buff *skb,
 	if (!sgout) {
 		nsg = skb_cow_data(skb, 0, &unused) + 1;
 		sgin = kmalloc_array(nsg, sizeof(*sgin), sk->sk_allocation);
-		if (!sgout)
 		sgout = sgin;
 	}