add_addr_accepted value is not printed if add_addr_signal value is 0.
Fix this properly looking for add_addr_accepted value, instead.
Fixes: 9c3be2c0ee ("ss: mptcp: add msk diag interface support")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>