sm: Fix a wrong key parameter in an exported private key file

* sm/export.c (sexp_to_kparms): Fix the computation of array[6],
which must be 'd mod (q-1)' but was 'p mod (q-1)'.

This bug is not serious but makes some consistency checks fail.
For example, 'openssl rsa -check' reports the following error:

$ gpgsm --out my.key --export-secret-key-raw 0xXXXXXXXX
$ openssl rsa -check -noout -inform DER -in my.key
RSA key error: dmq1 not congruent to d

Let me(wk) add this:

This bug was introduced with
right at the start of GnuPG 2.1 in July 2010. Before that (in 2.0) we
used gpg-protect-tool which got it right. We probably never noticed
this because gpgsm, and maybe other tools too, fix things up during
import.

• Fixes-commit: 91056b1976bfb7b755e53b1302f4ede2b5cbc05d
• Signed-off-by: Werner Koch <wk@gnupg.org>