mptcp: fix address removal logic in mptcp_pm_nl_rm_addr

Fix inverted WARN_ON_ONCE condition that prevented normal address
removal counter updates. The current code only executes decrement
logic when the counter is already 0 (abnormal state), while
normal removals (counter > 0) are ignored.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
Fixes: 6361139 ("mptcp: pm: remove '_nl' from mptcp_pm_nl_rm_addr_received")
Cc: stable@vger.kernel.org
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251118-net-mptcp-misc-fixes-6-18-rc6-v1-10-806d3781c95f@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Dwyane-Yan

net/mptcp/pm_kernel.c

@@ -672,7 +672,7 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 
 void mptcp_pm_nl_rm_addr(struct mptcp_sock *msk, u8 rm_id)
 {
-	if (rm_id && WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) {
+	if (rm_id && !WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) {
 		u8 limit_add_addr_accepted =
 			mptcp_pm_get_limit_add_addr_accepted(msk);