target/mips: add Octeon QMAC instructions

target/mips: add Octeon QMAC instructions

QMAC.0x and QMACS.0x multiply the selected signed Q15 halfword lane from
rs by rt<15:0> and accumulate the Q31 product into the Octeon HI/LO
accumulator state.

QMAC updates the full 64-bit HI/LO accumulator. QMACS saturates the
32-bit Q31 result in LO and keeps HI<0> as the sticky saturation flag.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
[PMD: Add min32/max32 in trans_QMACS()]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20260520172313.23777-24-philmd@linaro.org>