target/mips: Convert Vr54xx MACC* opcodes to decodetree

target/mips: Convert Vr54xx MACC* opcodes to decodetree

Convert the following Integer Multiply-Accumulate opcodes:

 * MACC         Multiply, accumulate, and move LO
 * MACCHI       Multiply, accumulate, and move HI
 * MACCHIU      Unsigned multiply, accumulate, and move HI
 * MACCU        Unsigned multiply, accumulate, and move LO

Since all opcodes are generated using the same pattern, we
add the gen_helper_mult_acc_t typedef and MULT_ACC() macro
to remove boilerplate code.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210808173018.90960-6-f4bug@amsat.org>