libhwc2.1: use vsync period to calculate expected vsync

When encountering an error from drmWaitVBlank, we should attempt to
calculate the expected vsync timestamp using the vsync period, rather
than the refresh rate.

Bug: 308095238
Test: fps switch, AoD in/out, On/Off
Change-Id: Ic0cc4d777727b009d2b6c2d4d4cee91f2a9ef0a5
3 files changed