ARM: imx: support arm power off in cpuidle for i.mx6sx

This patch introduces an independent cpuidle driver for
i.MX6SX, and supports arm power off in idle, totally
3 levels of cpuidle are supported as below:

1. ARM WFI;
2. SOC in WAIT mode;
3. SOC in WAIT mode + ARM power off.

ARM power off can save at least 5mW power.

This patch also replaces imx6q_enable_rbc with imx6_enable_rbc.

Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/mach-imx6sx.c

@@ -90,7 +90,7 @@ static void __init imx6sx_init_irq(void)
 
 static void __init imx6sx_init_late(void)
 {
-	imx6q_cpuidle_init();
+	imx6sx_cpuidle_init();
 
 	if (IS_ENABLED(CONFIG_ARM_IMX6Q_CPUFREQ))
 		platform_device_register_simple("imx6q-cpufreq", -1, NULL, 0);