cpu: Replace ENV_GET_CPU with env_cpu

Now that we have both ArchCPU and CPUArchState, we can define
this generically instead of via macro in each target's cpu.h.

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

linux-user/main.c

@@ -180,7 +180,7 @@ void init_task_state(TaskState *ts)
 
 CPUArchState *cpu_copy(CPUArchState *env)
 {
-    CPUState *cpu = ENV_GET_CPU(env);
+    CPUState *cpu = env_cpu(env);
     CPUState *new_cpu = cpu_create(cpu_type);
     CPUArchState *new_env = new_cpu->env_ptr;
     CPUBreakpoint *bp;