target/mips: Fix MSA MADDV.B opcode

target/mips: Fix MSA MADDV.B opcode

The result of the 'Vector Multiply and Add' opcode is incorrect
with Byte vectors. Probably due to a copy/paste error, commit
7a7a162adde mistakenly used the $wt (target register) instead
of $wd (destination register) as first operand. Fix that.

Cc: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
Fixes: 7a7a162adde ("target/mips: msa: Split helpers for MADDV.<B|H|W|D>")
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20211028210843.2120802-2-f4bug@amsat.org>