ARM: tegra: cpuidle: move the init function behind the suspend init function

One of the state of CPUidle on Tegra can power gate the CPU and the
vdd_cpu rail. But it depends on some configurations from DT and a common
hook function for different Tegra SoCs to power gate the CPU rail. And
these stuffs are initialized after common Tegra suspend init function. So
we move the CPUidle init behind the suspend init function. And making the
CPUidle driver more generic.

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