CI: cross-compile: riscv: Add RV64 machine with Zb* and Zk*

CI: cross-compile: riscv: Add RV64 machine with Zb* and Zk*

RISC-V already has a couple of routines to accelerate cryptographic
calculations using ISA extensions. Let's add a cross-compile target
that allows the CI to test this code.

The new defined machine is a rv64gc machine with
* all Bitmanip extensions (Zb*)
* all Scalar Crypto extensions (Zk*)

This selection matches the supported RISC-V extensions in OpenSSL.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20107)