ss: mptcp: subflow: display seq counters as decimal

ss: mptcp: subflow: display seq counters as decimal

This is similar to commit cfa70237 ("ss: mptcp: display seq related
counters as decimal") but for the subflow info this time. This is also
aligned with what is printed for TCP sockets.

That looks better to do the same with the subflow info (ss -ti), to
compare with the MPTCP info (ss -Mi), or for those who want to easily
count how many bytes have been exchanged between two runs without having
to think in hexa.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>