mptcp: options: rst: drop unused skb parameter

It was passed since its introduction in commit dc87efdb1a ("mptcp: add
mptcp reset option support"), but never used.

Simply removes it.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260605-net-next-mptcp-add-addr6-port-ts-v2-15-758e7ca73f4d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/options.c

@@ -744,7 +744,7 @@ static bool mptcp_established_options_mp_prio(struct sock *sk, int *size,
 	return true;
 }
 
-static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
+static noinline bool mptcp_established_options_rst(struct sock *sk,
 						   int *size,
 						   unsigned int remaining,
 						   struct mptcp_out_options *opts)
@@ -833,7 +833,7 @@ int mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 			remaining -= opt_size;
 		}
 		/* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
-		if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
+		if (mptcp_established_options_rst(sk, &opt_size, remaining, opts)) {
 			total_size += opt_size;
 			remaining -= opt_size;
 		}