clk: qcom: clock-cpu-8994: Add support for HW controlled clock trees

The MSM8994V2 SPM can support the disabling and enabling
of the CPU PLLs during power collapse and resume. In order
to ensure exclusivity of hardware versus software control,
perform the following steps before changing the rate of a
target cluster's clock:

1. Use PM QoS to prevent the low power mode that triggers
   hardware control.
2. Schedule an IPI on any core of the target cluster.
3. Wait for the IPI in (2) to finish execution.
4. Perform the clock switch.
5. Remove the PM QoS request in (1).

The steps above ensure that the target cluster does not
enter the low power mode that would enable hardware control
of the PLLs while the rate of the clock tree is being
switched.

Change-Id: I3f8b26a6d74128e63ceccf62462671845912f224
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>