ARM: substitute arch_idle()

Now that all implementations of arch_idle() are equivalent to cpu_do_idle()
we can just use the later directly and stop including mach/system.h.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-and-tested-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-omap2/pm44xx.c

@@ -173,7 +173,7 @@ static int __init pwrdms_setup(struct powerdomain *pwrdm, void *unused)
  * omap_default_idle - OMAP4 default ilde routine.'
  *
  * Implements OMAP4 memory, IO ordering requirements which can't be addressed
- * with default arch_idle() hook. Used by all CPUs with !CONFIG_CPUIDLE and
+ * with default cpu_do_idle() hook. Used by all CPUs with !CONFIG_CPUIDLE and
  * by secondary CPU with CONFIG_CPUIDLE.
  */
 static void omap_default_idle(void)
@@ -253,7 +253,7 @@ static int __init omap4_pm_init(void)
 	suspend_set_ops(&omap_pm_ops);
 #endif /* CONFIG_SUSPEND */
 
-	/* Overwrite the default arch_idle() */
+	/* Overwrite the default cpu_do_idle() */
 	arm_pm_idle = omap_default_idle;
 
 	omap4_idle_init();