Introduce quickwakeup technique.
Refer: http://www.elinux.org/Android_Power_Management
** Highly experimental **
The purpose of this feature is to drastically reduce the suspend/resume
time for device driver which needs to do periodic job.
In our use case (android smartphone), the system is most of the time in
suspend to RAM, and needs to send a low level command every 30s. With
current framework it takes about 500ms on omap3430 to resume the full
system, and then suspend again. With quickwakup feature, in the resume
process after resuming sysdev and re-enabling irq, the driver handler is
executed, and then it suspends again.
This new path takes 20ms for us, which leads to good power-saving.