RISC-V: Dump instruction without checking architecture support as usual.

Since QEMU have supported -Max option to to enable all normal extensions,
the dis-assembler should also add an option, -M,max to do the same thing.
For the instruction, which have overlapped encodings like zfinx, will not
be considered by the -M,max option.

opcodes/
	* riscv-dis.c (all_ext): New static boolean.  If set, disassemble
	without checking architectire string.
	(riscv_disassemble_insn): Likewise.
	(parse_riscv_dis_option_without_args): Recognized -M,max option.
binutils/
	* NEWS: Updated.