RISC-V: Add support for the Zvknh[a,b] ISA extensions

RISC-V: Add support for the Zvknh[a,b] ISA extensions

Zvknh[a,b] are parts of the vector crypto extensions.

This extension adds the following instructions:
- vsha2ms.vv
- vsha2c[hl].vv

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_multi_subset_supports): Add instruction
	class support for Zvknh[a,b].
	(riscv_multi_subset_supports_ext): Likewise.

gas/ChangeLog:

	* testsuite/gas/riscv/zvknha.d: New test.
	* testsuite/gas/riscv/zvknha_zvknhb.s: New test.
	* testsuite/gas/riscv/zvknhb.d: New test.

include/ChangeLog:

	* opcode/riscv-opc.h (MATCH_VSHA2CH_VV): New.
	(MASK_VSHA2CH_VV): New.
	(MATCH_VSHA2CL_VV): New.
	(MASK_VSHA2CL_VV): New.
	(MATCH_VSHA2MS_VV): New.
	(MASK_VSHA2MS_VV): New.
	(DECLARE_INSN): New.
	* opcode/riscv.h (enum riscv_insn_class): Add instruction class
	support for Zvknh[a,b].

opcodes/ChangeLog:

	* riscv-opc.c: Add Zvknh[a,b] instructions.

Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>