target/mips: Extract MSA translation routines

Extract 2200 lines from the huge translate.c to a new file,
'msa_translate.c'. As there are too many inter-dependencies
we don't compile it as another object yet, but keep including
it in the big translate.o. We gain in code maintainability.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201120210844.2625602-5-f4bug@amsat.org>
Tested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>

target/mips/meson.build

@@ -8,6 +8,7 @@ mips_ss.add(when: 'CONFIG_TCG', if_true: files(
   'fpu_helper.c',
   'lmmi_helper.c',
   'msa_helper.c',
+  'msa_translate.c',
   'op_helper.c',
   'tlb_helper.c',
   'translate.c',