RISC-V: Implement ZKNH extension

RISC-V: Implement ZKNH extension

This patch supports Zknh extension.
It includes instruction's machine description and built-in funtions.

gcc/ChangeLog:

	* config/riscv/crypto.md (riscv_sha256sig0_<mode>): Add ZKNH's instructions.
	(riscv_sha256sig1_<mode>): New.
	(riscv_sha256sum0_<mode>): New.
	(riscv_sha256sum1_<mode>): New.
	(riscv_sha512sig0h): New.
	(riscv_sha512sig0l): New.
	(riscv_sha512sig1h): New.
	(riscv_sha512sig1l): New.
	(riscv_sha512sum0r): New.
	(riscv_sha512sum1r): New.
	(riscv_sha512sig0): New.
	(riscv_sha512sig1): New.
	(riscv_sha512sum0): New.
	(riscv_sha512sum1): New.
	* config/riscv/riscv-builtins.cc (AVAIL): And ZKNH's AVAIL.
	* config/riscv/riscv-scalar-crypto.def (RISCV_BUILTIN): And ZKNH's
	built-in functions.
	(DIRECT_BUILTIN): Add new.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/zknh-sha256.c: New test.
	* gcc.target/riscv/zknh-sha512-32.c: New test.
	* gcc.target/riscv/zknh-sha512-64.c: New test.

Co-Authored-By: SiYu Wu <siyu@isrc.iscas.ac.cn>