qcom: cpu_ops: Provide callback API for cpu suspend/resume framework.

Cpu suspend/resume framework does the register context save/restore and
allows users to provide the callback to perform ARCH specific job while cpu
going to suspend.
Register msm_pm_collapse with cpu_ops for cpu suspend/resume to callback
msm_pm_collapse during idle low power modes.

Change-Id: I44db75f5e69354358750eda3261eef8817908ed4
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>