target/ppc: Tidy exception vs exit_tb

We do not need to emit an exit_tb after an exception,
as the latter will exit via longjmp.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Message-Id: <20210517205025.3777947-7-matheus.ferst@eldorado.org.br>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

target/ppc/translate.c

@@ -4648,8 +4648,9 @@ static void gen_lookup_and_goto_ptr(DisasContext *ctx)
         } else if (sse & (CPU_SINGLE_STEP | CPU_BRANCH_STEP)) {
             uint32_t excp = gen_prep_dbgex(ctx);
             gen_exception(ctx, excp);
+        } else {
+            tcg_gen_exit_tb(NULL, 0);
         }
-        tcg_gen_exit_tb(NULL, 0);
     } else {
         tcg_gen_lookup_and_goto_ptr();
     }