Rely on SoftHSM being installed correctly with a p11-kit .module file

Rely on SoftHSM being installed correctly with a p11-kit .module file

I don't actually remember why I added my own; it *ought* to be installed
correctly by the distribution's packaging of SoftHSM.

There was a brief discussion about my hard-coded version being
Fedora-specific, followed by a suggestion that I could pick up the
proper path from and existing module file, followed by the realisation
that said existing module file would suffice anyway. So just require it.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>