omap4: hotplug: Add basic CPU hotplug support

This patch adds cpu hotplug support for OMAP4430. Only CPU inactive
state is supported as a low power state in the basic hot-plug support

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>