stagefright: Remove the HAL3 limitation from the video reference clock selection

Usage of boot-time as the timestamp reference isn't necessarily limited to
HAL3. A single property check for media.camera.ts.monotonic is enough to
cover all cases.

RM-290
Change-Id: Ic56dbcc6ba32c25bccde6dd0bbf07d4c918af43e
(cherry picked from commit 2071f205)