target/mips: Re-introduce OPC_ADDUH_QB_DSP and OPC_MUL_PH_DSP

target/mips: Re-introduce OPC_ADDUH_QB_DSP and OPC_MUL_PH_DSP

There is no issue having multiple enum declarations with
the same value. As we are going to remove the OPC_MULT_G_2E
definition in few commits, restore the OPC_ADDUH_QB_DSP and
OPC_MUL_PH_DSP definitions and use them where they belong.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20241026175349.84523-4-philmd@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>