staging: crypto: skein: allow building statically

These are the minimum changes required to get the code to build
statically in the kernel.  It's necessary to do this first so that we
can empirically determine that future cleanup patches aren't changing
the generated object code.

Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>