s390/crypto: fix compile error for ChaCha20 module

The clgfi instruction used within the ChaCha20 assembly is only
available for z9-109 and newer machines, and therefore this will
generate a compile error if compiled e.g. with MARCH_Z900.

Given that the assembler code will only be executed on machines with
vector instructions, which became much later available than z9-109,
use insn notation to generate the clgfi instruction, and avoid compile
errors due to unknown instructions.

Fixes: b087dfab ("s390/crypto: add SIMD implementation for ChaCha20")
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>