RISC-V: Make "fli.h" available to 'Zvfh' + 'Zfa'

RISC-V: Make "fli.h" available to 'Zvfh' + 'Zfa'

The documentation of the 'Zfa' extension states that "fli.h" is available
"if the Zfh or Zvfh extension is implemented" (both the latest and the
oldest editions are checked).

This fact was not reflected in Binutils ('Zvfh' implies 'Zfhmin', not full
'Zfh' extension and "fli.h" required 'Zfh' and 'Zfa' extensions).
This commit makes "fli.h" also available when both 'Zfa' and 'Zvfh'
extensions are implemented.

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_multi_subset_supports): Add new
	instruction class handling.
	(riscv_multi_subset_supports_ext): Likewise.

gas/ChangeLog:

	* testsuite/gas/riscv/zfa-zvfh.s: New test.
	* testsuite/gas/riscv/zfa-zvfh.d: Ditto.

include/ChangeLog:

	* opcode/riscv.h (enum riscv_insn_class): Add new instruction
	class.

opcodes/ChangeLog:

	* riscv-opc.c (riscv_opcodes): Change instruction class of "fli.h"
	from INSN_CLASS_ZFH_AND_ZFA to new INSN_CLASS_ZFH_OR_ZVFH_AND_ZFA.