scd:p15: Prepare AODF parsing for other authentication types.

* scd/app-p15.c (auth_type_t): New.
(struct aodf_object_s): Add field auth_type.
(read_ef_aodf): Distinguish between pin and authkey types.  Include
the authtype in the verbose mode diags.

Note that the bulk of changes are just indentation changes. There
should be no functional change.

(cherry picked from commit e387cc97c82313457e4f79729a137e5871891bc1)

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