With an eye toward having this data replace the gen_opc_* arrays
that each target collects in order to enable restore_state_from_tb.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>