Merge remote-tracking branch 'remotes/philmd/tags/mips-20210625' into staging

MIPS patches queue

Various fixes:
- Potential integer overflow (CID 1452921)
- Invalid emulation of nanoMIPS BPOSGE32 opcode
- Missing exception when DINSV opcode used with DSP disabled
- Do not abort but emit exception for invalid BRANCH opcodes
- TCG temporary leaks

Housekeeping:
- Remove dead code / comments
- Restrict few files to TCG, declarations to sysemu
- Merge MSA32 and MSA64 decodetree definitions

# gpg: Signature made Fri 25 Jun 2021 10:22:20 BST
# gpg:                using RSA key FAABE75E12917221DCFD6BB2E3E32C2CDEADC0DE
# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [full]
# Primary key fingerprint: FAAB E75E 1291 7221 DCFD  6BB2 E3E3 2C2C DEAD C0DE

* remotes/philmd/tags/mips-20210625:
  target/mips: Merge msa32/msa64 decodetree definitions
  target/mips: Remove pointless gen_msa()
  target/mips: Optimize regnames[] arrays
  target/mips: Constify host_to_mips_errno[]
  target/mips: fix emulation of nanoMIPS BPOSGE32 instruction
  target/mips: Remove microMIPS BPOSGE32 / BPOSGE64 unuseful cases
  target/mips: Remove SmartMIPS / MDMX unuseful comments
  target/mips: Restrict some system specific declarations to sysemu
  target/mips: Move translate.h to tcg/ sub directory
  target/mips: Move TCG trace events to tcg/ sub directory
  target/mips: Do not abort on invalid instruction
  target/mips: Raise exception when DINSV opcode used with DSP disabled
  target/mips: Fix more TCG temporary leaks in gen_pool32a5_nanomips_insn
  target/mips: Fix TCG temporary leaks in gen_pool32a5_nanomips_insn()
  target/mips: Fix potential integer overflow (CID 1452921)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>