RISC-V: Add support for the Zvkg ISA extension

RISC-V: Add support for the Zvkg ISA extension

Zvkg is part of the vector crypto extensions.

This extension adds the following instructions:
- vghsh.vv
- vgmul.vv

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_multi_subset_supports): Add instruction
	class support for Zvkg.
	(riscv_multi_subset_supports_ext): Likewise.

gas/ChangeLog:

	* testsuite/gas/riscv/zvkg.d: New test.
	* testsuite/gas/riscv/zvkg.s: New test.

include/ChangeLog:

	* opcode/riscv-opc.h (MATCH_VGHSH_VV): New.
	(MASK_VGHSH_VV): New.
	(MATCH_VGMUL_VV): New.
	(MASK_VGMUL_VV): New.
	(DECLARE_INSN): New.
	* opcode/riscv.h (enum riscv_insn_class): Add instruction class
	support for Zvkg.

opcodes/ChangeLog:

	* riscv-opc.c: Add Zvkg instructions.

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