ueventd.rc: Reduce permissions for /dev/dma_heap/system to 444

Jeffrey Vander Stoep noted the permissions for the system dmabuf
heap should be 444 instead of 666, as we only need to open and
call ioctl on the device.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I650c9fabfffd1eac5f59bbc7fa1e0ae1f5646bd9
diff --git a/rootdir/ueventd.rc b/rootdir/ueventd.rc
index 42229bd..5ed9d4d 100644
--- a/rootdir/ueventd.rc
+++ b/rootdir/ueventd.rc
@@ -46,7 +46,7 @@
 /dev/vndbinder            0666   root       root
 
 /dev/pmsg0                0222   root       log
-/dev/dma_heap/system      0666   system     system
+/dev/dma_heap/system      0444   system     system
 
 # kms driver for drm based gpu
 /dev/dri/*                0666   root       graphics