target/ppc: Make divd[u] handler method decodetree compatible

This is like commit 86e6202a57 ("target/ppc: Make divw[u] handler
method decodetree compatible."), but for gen_op_arith_divd().

Cc: qemu-stable@nongnu.org
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

target/ppc/translate.c

@@ -1820,7 +1820,7 @@ static inline void gen_op_arith_divd(DisasContext *ctx, TCGv ret,
         tcg_gen_or_tl(cpu_so, cpu_so, cpu_ov);
     }
 
-    if (unlikely(Rc(ctx->opcode) != 0)) {
+    if (unlikely(compute_rc0)) {
         gen_set_Rc0(ctx, ret);
     }
 }