s390x: support CPACF sha3/shake performance improvements

[jschmidb]

On newer machines the SHA3/SHAKE performance of CPACF instructions KIMD and KLMD can be enhanced by using additional modifier bits. This allows the application to omit initializing the ICV, but also affects the internal processing of the instructions. Performance is mostly gained when processing short messages.

The new CPACF feature is backwards compatible with older machines, i.e. the new modifier bits are ignored on older machines. However, to save the ICV initialization, the application must detect the MSA level and omit the ICV initialization only if this feature is supported.

[ifranzki]

@t8m Friendly ping :-)

[openssl-machine]

This pull request is ready to merge

[t8m]

Merged to the master branch. Thank you for your contribution.