power: qcom: apm: support switching APC clock sources via the secure world

Add support to switch the APC0 and APC1 clock sources to GPLL0 via
the secure world before VDD_APCC to VDD_MX or VDD_MX to VDD_APCC APM
transitions begin and to switch back to the original clock source
after the APM sequence completes. This is necessary to guarantee
stable operation of certain CPUSS blocks.

Change-Id: I348a9dec7e35cfbc217e19f864794af999167108
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>