chelsio/chtls: fix a double free in chtls_setkey()

The "skb" is freed by the transmit code in cxgb4_ofld_send() and we
shouldn't use it again.  But in the current code, if we hit an error
later on in the function then the clean up code will call kfree_skb(skb)
and so it causes a double free.

Set the "skb" to NULL and that makes the kfree_skb() a no-op.

Fixes: d25f2f71 ("crypto: chtls - Program the TLS session Key")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/X8ilb6PtBRLWiSHp@mwandaSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_hw.c

@@ -391,6 +391,7 @@ int chtls_setkey(struct chtls_sock *csk, u32 keylen,
 	csk->wr_unacked += DIV_ROUND_UP(len, 16);
 	enqueue_wr(csk, skb);
 	cxgb4_ofld_send(csk->egress_dev, skb);
+	skb = NULL;
 
 	chtls_set_scmd(csk);
 	/* Clear quiesce for Rx key */