target/m68k: Clean up local variable shadowing

target/m68k: Clean up local variable shadowing

Fix:

  target/m68k/translate.c:828:18: error: declaration shadows a local variable [-Werror,-Wshadow]
            TCGv tmp = tcg_temp_new();
                 ^
  target/m68k/translate.c:801:15: note: previous declaration is here
    TCGv reg, tmp, result;
              ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-ID: <20230904161235.84651-6-philmd@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>