suspend mode enter

cpu_do_idle in this project is mapped to cpu_v6_do_idle in
/kernel/arch/arm/mm/proc-v6.S by cpu-single.h

> > In /kernel/kernel/power/main.c, the final place to go to suspend mode:
> >
> > static int suspend_enter(suspend_state_t state)
> > {
> > ...
> > if (!suspend_test(TEST_CORE))
> > error = suspend_ops->enter(state);
> > ...
> > }
> >
> > The suspend_ops is set in /kernel/arch/arm/mach-mx37/pm.c
> > static int __init mx37_pm_init(void)
> >
> > The cpu low power functions are in /kernel/arch/arm/mach-mx37/system.c
> > void mxc_cpu_lp_set(enum mxc_cpu_pwr_mode mode)
> >
> >