gpg: Rename two card related functions in card-util.

* g10/card-util.c (ask_card_rsa_keysize): Rename to ask_card_keyattr.
(do_change_rsa_keysize): Rename to do_change_keyattr.

We want to support other algos than RSA and thus we need a better name
for the functions.

• Signed-off-by: Werner Koch <wk@gnupg.org>