target/mips: Define R5900 ISA, MMI ASE, and R5900 CPU preprocessor constants

target/mips: Define R5900 ISA, MMI ASE, and R5900 CPU preprocessor constants

The R5900 implements the 64-bit MIPS III instruction set except
DMULT, DMULTU, DDIV, DDIVU, LL, SC, LLD and SCD. The MIPS IV
instructions MOVN, MOVZ and PREF are implemented. It has the
R5900-specific three-operand instructions MADD, MADDU, MULT and
MULTU as well as pipeline 1 versions MULT1, MULTU1, DIV1, DIVU1,
MADD1, MADDU1, MFHI1, MFLO1, MTHI1 and MTLO1. A set of 93 128-bit
multimedia instructions specific to the R5900 is also implemented.

The Toshiba TX System RISC TX79 Core Architecture manual:

https://wiki.qemu.org/File:C790.pdf

describes the C790 processor that is a follow-up to the R5900. There
are a few notable differences in that the R5900 FPU

- is not IEEE 754-1985 compliant,
- does not implement double format, and
- its machine code is nonstandard.

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Fredrik Noring <noring@nocrew.org>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>