graphics: use FIFO scheduler in IComposer

Make IComposer default implementation use the same process scheduler
as SurfaceFlinger does.

Bug: 35210697
Test: manual
Change-Id: Ie2ebe1d3fd26505984d9f6c33d63b5db36b0b64a
diff --git a/graphics/composer/2.1/default/android.hardware.graphics.composer@2.1-service.rc b/graphics/composer/2.1/default/android.hardware.graphics.composer@2.1-service.rc
index fc21d59..9548d41 100644
--- a/graphics/composer/2.1/default/android.hardware.graphics.composer@2.1-service.rc
+++ b/graphics/composer/2.1/default/android.hardware.graphics.composer@2.1-service.rc
@@ -2,4 +2,5 @@
     class hal
     user system
     group graphics drmrpc readproc
+    capabilities SYS_NICE
     onrestart restart surfaceflinger