Allow dumpstate to read DMA-BUF sysfs stats

These permissions are required for dumpstate to read the DMA-BUF sysfs
stats present at /sys/kernel/dmabuf/buffers

Bug: 167709539
Test: adb shell am bug-report
Change-Id: I1c00843775452b7a7aa39b059e1d77d77aed1e9c
diff --git a/private/dumpstate.te b/private/dumpstate.te
index 2b7b228..16f4add 100644
--- a/private/dumpstate.te
+++ b/private/dumpstate.te
@@ -51,6 +51,7 @@
 allow dumpstate debugfs_wakeup_sources:file r_file_perms;
 allow dumpstate dev_type:blk_file getattr;
 allow dumpstate webview_zygote:process signal;
+allow dumpstate sysfs_dmabuf_stats:file r_file_perms;
 dontaudit dumpstate update_engine:binder call;
 
 # Read files in /proc