Surfacefinger: Set HWC Callback to SCHED_FIFO

IComposerCallback is on critical path to correct vsync, this CL makes
the callback runs in SCHED_FIFO to minimize scheduling latency.

Bug: 133241520
Test: Build
Change-Id: Ifda73c4b33771763c2b58b25d32b805ed602369a
1 file changed