target/sparc: convert to TranslatorOps

target/sparc: convert to TranslatorOps

Notes:

- Moved the cross-page check from the end of translate_insn to
  init_disas_context.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>