ARM: tegra: make tegra_resume can work with current and later chips

Because the CPU0 was the first up and the last down core when cluster
power up/down or platform suspend. So only CPU0 needs the rest of the
functions to reset flow controller and re-enable SCU and L2. We also
move the L2 init function for Cortex-A15 to there. The secondery CPU
can just call cpu_resume.

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