scd:p15: Run a keygrip_from_prkdf before verify_pin

* scd/app-p15.c (do_sign): Move keygrip_from_prkdf before PIN
verification.
(do_decipher): Add keygrip_from_prkdf.

This is required because that function may change the current file
which is set by prepare_verify_pin right before MSE. HAs alredy been
done on the backport to 2.2

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