target/mips: Convert MSA 3R instruction format to decodetree (part 2/4)

target/mips: Convert MSA 3R instruction format to decodetree (part 2/4)

Convert 3-register operations to decodetree.

Per the Encoding of Operation Field for 3R Instruction Format'
(Table 3.25), these instructions are not defined for the BYTE
format. Therefore the TRANS_DF_iii_b() macro returns 'false'
in that case, because no such instruction is decoded.

Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211028210843.2120802-22-f4bug@amsat.org>