clk: msm: osm: add support for APM crossover corner

Add support to determine the APM threshold corner via open-loop
voltages in the VDD regulator OPP table. The threshold corner
is used by OSM to determine the APM supply for each DCVS setpoint.
The crossover corner is used by OSM to request a specific voltage
during the APM switch transition.

CRs-Fixed: 1021656 1030444
Change-Id: Iac04f6db8e85b3651a33b6c9bff667365cae891d
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>