gpg: Improve 'General key info' line of --card-status.

* g10/keylist.c (print_pubkey_info): Print either "pub" or "sub".

This now prints "sub" if the first used card key is actually a subkey.

(backported from master 874ef16e70ab750db7b153f17a7e859a0db6a2f1)

• Signed-off-by: Werner Koch <wk@gnupg.org>
• GnuPG-bug-id: T2079