RISC-V: Add support for the 'Zihintntl' extension

RISC-V: Add support for the 'Zihintntl' extension

This commit adds 'Zihintntl' extension and its hint instructions.

This is based on:
<https://github.com/riscv/riscv-isa-manual/commit/0dc91f505e6da7791d5a733c553e6e2506ddcab5>,
the first ISA Manual noting that the 'Zihintntl' extension is ratified.

Note that compressed 'Zihintntl' hints require either 'C' or
'Zca' extension.

Co-authored-by: Nelson Chu <nelson@rivosinc.com>
bfd/ChangeLog:

	* elfxx-riscv.c (riscv_supported_std_z_ext): Add 'Zihintntl'
	standard hint 'Z' extension.
	(riscv_multi_subset_supports): Support new instruction classes.
	(riscv_multi_subset_supports_ext): Likewise.

gas/ChangeLog:

	* testsuite/gas/riscv/zihintntl.s: New test for 'Zihintntl'
	including auto-compression without C prefix and explicit C prefix.
	* testsuite/gas/riscv/zihintntl.d: Likewise.
	* testsuite/gas/riscv/zihintntl-na.d: Likewise.
	* testsuite/gas/riscv/zihintntl-base.s: New test for correspondence
	between 'Zihintntl' and base 'I' or 'C' instructions.
	* testsuite/gas/riscv/zihintntl-base.d: Likewise.

include/ChangeLog:

	* opcode/riscv.h (enum riscv_insn_class): Add new instruction
	classes: INSN_CLASS_ZIHINTNTL and INSN_CLASS_ZIHINTNTL_AND_C.
	(MASK_NTL_P1, MATCH_NTL_P1, MASK_NTL_PALL,
	MATCH_NTL_PALL, MASK_NTL_S1, MATCH_NTL_S1, MASK_NTL_ALL,
	MATCH_NTL_ALL, MASK_C_NTL_P1, MATCH_C_NTL_P1, MASK_C_NTL_PALL,
	MATCH_C_NTL_PALL, MASK_C_NTL_S1, MATCH_C_NTL_S1, MASK_C_NTL_ALL,
	MATCH_C_NTL_ALL): New.

opcodes/ChangeLog:

	* riscv-opc.c (riscv_opcodes): Add instructions from the
	'Zihintntl' extension.