cpu: Introduce cpu_set_cpustate_pointers

Consolidate some boilerplate from foo_cpu_initfn.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/hppa/cpu.c

@@ -134,7 +134,7 @@ static void hppa_cpu_initfn(Object *obj)
     HPPACPU *cpu = HPPA_CPU(obj);
     CPUHPPAState *env = &cpu->env;
 
-    cs->env_ptr = env;
+    cpu_set_cpustate_pointers(cpu);
     cs->exception_index = -1;
     cpu_hppa_loaded_fr0(env);
     cpu_hppa_put_psw(env, PSW_W);