SF: Fix getting vsync period in SF and Scheduler

SF and Scheduler rely on primary refresh rate configuration
from init. If non primary display becomes vsync source,
make call to getVsyncPeriodFromHWC to get correct vsync
source and to get the correct vsync period. In addition,
cache the vsync period in DisplayDevice until there is a
mode switch or power mode change.

CRs-Fixed: 3004697
Change-Id: I4810b4df8cede54c80ea3b03a32e294eecf4b07c
8 files changed