MIPS/BFD: Consistently mark the LSI CW4010 as a MIPS II processor

MIPS/BFD: Consistently mark the LSI CW4010 as a MIPS II processor

Make BFD agree with GAS and mark the LSI MiniRISC CW4010 processor core
(for an odd reason referred to as LSI R4010 across our code base) as a
MIPS II processor in BFD as well, fixing a bug that has been there since
forever and addressing linker warnings like:

$ as -m4010 empty.s -o 4010.o
$ ld -r 4010.o -o 4010-r.o
ld: 4010.o: warning: Inconsistent ISA between e_flags and .MIPS.abiflags
$

due to the ISA level being recorded as MIPS III in ELF file header's
`e_flags' vs MIPS II in the MIPS ABI Flags section:

$ readelf -Ah 4010.o
ELF Header:
  Magic:   7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, big endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           MIPS R3000
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          348 (bytes into file)
  Flags:                             0x20821000, 4010, o32, mips3
  Size of this header:               52 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           40 (bytes)
  Number of section headers:         11
  Section header string table index: 10
Attribute Section: gnu
File Attributes
  Tag_GNU_MIPS_ABI_FP: Hard float (double precision)

MIPS ABI Flags Version: 0

ISA: MIPS2
GPR size: 32
CPR1 size: 32
CPR2 size: 0
FP ABI: Hard float (double precision)
ISA Extension: LSI R4010
ASEs:
	None
FLAGS 1: 00000000
FLAGS 2: 00000000
$

Available documentation[1][2] clearly indicates the LSI CW4010 processor
is only backwards compatible with the MIPS R4000 processor as far as the
latter's 32-bit instructions are concerned and consequently can only be
considered a MIPS II ISA implementation (with vendor extensions).

This fixes an LD testsuite failure:

FAIL: MIPS incompatible objects:  "-march=r4010 -32"      "-march=r4650 -32"

triggered for the `mips-sgi-irix5' and `mips-sgi-irix6' targets.

References:

[1] Paul Cobb, Bob Caulk, Joe Cesana, "The MiniRISC CW4010: A
    Superscalar MIPS Processor ASIC Core", LSI Logic, July 1995,
    presented at Hot Chips VII, Stanford University, Stanford,
    California, August 1995

[2] "MiniRISC MR4010 Superscalar Microprocessor Reference Device", LSI
    Logic, November 1996, Doc. No. DB09-000028-00, Order No. C15017

	bfd/
	* cpu-mips.c (arch_info_struct): Mark the 4010 32-bit.
	* elfxx-mips.c (mips_set_isa_flags) <bfd_mach_mips4010>: Set
	E_MIPS_ARCH_2 rather than E_MIPS_ARCH_3 in `e_flags'.
	(mips_mach_extensions): Mark `bfd_mach_mips4010' as extending
	`bfd_mach_mips6000' rather than `bfd_mach_mips4000'.

	ld/
	* testsuite/ld-mips-elf/lsi-4010-isa.d: New test.
	* ld/testsuite/ld-mips-elf/mips-elf.exp: Run the new test.