Arc assembler: Convert nps400 from a machine type to an extension.

Arc assembler: Convert nps400 from a machine type to an extension.

gas	* config/tc-arc.c (check_cpu_feature, md_parse_option):
	Add nps400 option and feature. Add check for nps400
	feature. Refactor existing checks to check subclass before
	feature enablement.
	(md_show_usage): Document flags for NPS-400 and add some other
	undocumented flags.
	(cpu_type): Remove nps400 CPU type entry
	(check_zol): Remove bfd_mach_arc_nps400 case.
	(md_show_usage): Add help on -mcpu=nps400.
	(cpu_types): Add entry for nps400 as arc700 plus nps400 extension
	set.
	* doc/c-arc.texi: Document the -mnps400, -mspfp, -mdpfp, and
	-fpuda flags.  Document -mcpu=nps400.
	* testsuite/gas/arc/nps-400-0.d: Use -mcpu=arc700 -mnps400. Change
	expected flags to match ARC700 instead of NPS400.
	* testsuite/gas/arc/nps-400-1.d: Use -mcpu=arc700 -mnps400.
	* testsuite/gas/arc/nps-400-2.d: Likewise.
	* testsuite/gas/arc/nps-400-3.d: Likewise.
	* testsuite/gas/arc/nps-400-4.d: Likewise.
	* testsuite/gas/arc/nps-400-5.d: Likewise.
	* testsuite/gas/arc/nps-400-6.d: Likewise.
	* testsuite/gas/arc/nps-400-7.d: Likewise.
	* testsuite/gas/arc/textinsn2op01.s: Change opcode of myinsn to
	avoid clash with cbba instruction.
	* testsuite/gas/arc/textinsn2op01.d: Likewise.
	* testsuite/gas/arc/textinsn3op.d: Likewise.
	* testsuite/gas/arc/textinsn3op.s: Likewise.
	* testsuite/gas/arc/nps-400-0.d: Test using NPS-400 using
	-mcpu=nps400 as an alternative to -mcpu=arc700 -mnps400 flags.

binutils* readelf.c (decode_ARC_machine_flags): Remove E_ARC_MACH_NPS400
	case.

ld	* testsuite/ld-arc/nps-1a.d: Use -mcpu=arc700 -mnps400.
	* testsuite/ld-arc/nps-1b.d: Likewise.

include	* opcode/arc.h: Add nps400 extension and instruction
	subclass.
	Remove ARC_OPCODE_NPS400
	* elf/arc.h: Remove E_ARC_MACH_NPS400

opcodes	* arc-dis.c (arc_insn_length): Add comment on instruction length.
	Use same method for determining	instruction length on ARC700 and
	NPS-400.
	(arc_insn_length, print_insn_arc): Remove bfd_mach_arc_nps400.
	* arc-nps400-tbl.h: Make all nps400 instructions ARC700 instructions
	with the NPS400 subclass.
	* arc-opc.c: Likewise.

bfd	* archures.c: Remove bfd_mach_arc_nps400.
	* bfd-in2.h: Likewise.
	* cpu-arc.c (arch_info_struct): Likewise.
	* elf32-arc.c (arc_elf_object_p, arc_elf_final_write_processing):
	Likewise.