package/strongswan: add tools option deprecation notice

It's now a split option with pki and scep, with some other tools being
deprecated upstream so select both when tools was selected to get as
close as possible.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>