Update SurfaceFlinger FIFO configuration.

- move SurfaceFlinger main thread to prio 2
- drop EventThread from FIFO but not SFEventThread, which is still FIFO
prio 1
- make DispSyncThread FIFO, prio 1

bug 30481949

Change-Id: Ifedccfbf3cf144ffad030109849a924dddae8d09
diff --git a/services/surfaceflinger/main_surfaceflinger.cpp b/services/surfaceflinger/main_surfaceflinger.cpp
index 543d0c7..53a63bd 100644
--- a/services/surfaceflinger/main_surfaceflinger.cpp
+++ b/services/surfaceflinger/main_surfaceflinger.cpp
@@ -64,7 +64,7 @@
     sm->addService(String16(GpuService::SERVICE_NAME), gpuservice, false);
 
     struct sched_param param = {0};
-    param.sched_priority = 1;
+    param.sched_priority = 2;
     if (sched_setscheduler(0, SCHED_FIFO, &param) != 0) {
         ALOGE("Couldn't set SCHED_FIFO");
     }