ARM: tegra: shut off the CPU rail when the last CPU in suspend

When the last CPU core in suspend, the CPU power rail can be turned off
by setting flags to flow controller. Then the flow controller will inform
PMC to turn off the CPU rail when the last CPU goes into suspend.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>