cipher: Fix regression in Padlock support.

* cipher/rijndael.c (do_setkey): Remove dummy padlock key generation case
and use the standard one.

This is really a brown paper bag bug. I should have been able to
fix it by a bit of code staring or bi-secting it myself. Instead
Rafaël Carré did this and with the donation of a VIA nano board from
Stefan Krüger. Thanks to both of you.

(regression since commit b825c5db17292988d261fefdc83cbc43d97d4b02)

(cherry picked from commit f1f016855418aae561ede4472590d45a24ab4476)

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