arm/imx: remove cpu_is_xxx() from arch_idle()

This patch adds an idle hook imx_idle to be called in arch_idle().
Any soc that needs a customized idle implementation other than
cpu_do_idle() can set up this hook in soc specific call.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/mach-mx5/mm.c b/arch/arm/mach-mx5/mm.c
index baea6e5..379593e 100644
--- a/arch/arm/mach-mx5/mm.c
+++ b/arch/arm/mach-mx5/mm.c
@@ -21,6 +21,11 @@
 #include <mach/devices-common.h>
 #include <mach/iomux-v3.h>
 
+static void imx5_idle(void)
+{
+	mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
+}
+
 /*
  * Define the MX51 memory map.
  */
@@ -56,6 +61,7 @@
 	mxc_set_cpu_type(MXC_CPU_MX51);
 	mxc_iomux_v3_init(MX51_IO_ADDRESS(MX51_IOMUXC_BASE_ADDR));
 	mxc_arch_reset_init(MX51_IO_ADDRESS(MX51_WDOG1_BASE_ADDR));
+	imx_idle = imx5_idle;
 }
 
 void __init mx53_map_io(void)