sepolicy: add persist_block_device type

* This is likely defined in several device trees, but not all
  remove it from your device trees if we're going to write rules
  for it here.

Change-Id: I1dda04647d36db52525a3d57b485860dfe3eeb30
diff --git a/sepolicy/qcom/device.te b/sepolicy/qcom/device.te
new file mode 100644
index 0000000..9e49627
--- /dev/null
+++ b/sepolicy/qcom/device.te
@@ -0,0 +1 @@
+type persist_block_device, dev_type;