target/mips: Add emulation of MXU instructions for 32-bit load/store

target/mips: Add emulation of MXU instructions for 32-bit load/store

Add support for emulating:
- S32LDDV and S32LDDVR
- S32STD and S32STDR
- S32STDV and S32STDVR
MXU instructions.

Add support for emulating MXU instructions with address register
post-modify counterparts:
- S32LDI and S32LDIR
- S32LDIV and S32LDIVR
- S32SDI and S32SDIR
- S32SDIV and S32SDIVR

Refactor support for emulating the S32LDD and S32LDDR instructions.

Signed-off-by: Siarhei Volkau <lis8215@gmail.com>
Message-Id: <20230608104222.1520143-2-lis8215@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>