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/cris/cpu_loop.c

@@ -83,7 +83,7 @@ void cpu_loop(CPUCRISState *env)
 
 void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
 {
-    CPUState *cpu = ENV_GET_CPU(env);
+    CPUState *cpu = env_cpu(env);
     TaskState *ts = cpu->opaque;
     struct image_info *info = ts->info;