arm64: kernel: Adding arch_cpu_idle_enter/exit()

arm64: kernel: Adding arch_cpu_idle_enter/exit()

Adding idle_notifier_call_chain calls in arch_cpu_idle_enter/exit(),
since these are required for cpufreq_interactive.

(see also 6e97e69a7735d3fdc231cb50fe055dbaf1faec48)

Change-Id: I2dc5ead78608350a010bc0ea2a1d139c8867620a
Signed-off-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Reviewed-on: http://git-master/r/351085
GVS: Gerrit_Virtual_Submit
Reviewed-by: Krishna Sitaraman <ksitaraman@nvidia.com>
Tested-by: Krishna Sitaraman <ksitaraman@nvidia.com>
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>