ARM: tegra: moving the clock gating procedure to tegra_cpu_kill

The tegra_cpu_die was be executed by the CPU itslf. So the clock gating
procedure won't be executed after the CPU hardware shutdown code. Moving
the clock gating procedure to tegra_cpu_kill that will be run by another
CPU after the CPU died.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>