mptcp: pm: use ipv6_addr_equal in addresses_equal

mptcp: pm: use ipv6_addr_equal in addresses_equal

Use ipv6_addr_equal() to check whether two IPv6 addresses are equal in
mptcp_addresses_equal().

This is more appropriate than using !ipv6_addr_cmp().

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250221-net-next-mptcp-pm-misc-cleanup-3-v1-7-2b70ab1cee79@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>