msm8916: Add selinux-policy to make boot_control work in update_engine.

The msm8916 boot_control implementation modifies the partition table
when managing A/B.

BUG=24675877

Change-Id: I649c9193b3f7a0d5c83b7959b9b54fcb7a00997e
diff --git a/soc/msm8916/sepolicy/update_engine.te b/soc/msm8916/sepolicy/update_engine.te
new file mode 100644
index 0000000..2bb5061
--- /dev/null
+++ b/soc/msm8916/sepolicy/update_engine.te
@@ -0,0 +1,7 @@
+# This file contains msm8916-specific SELinux policy for
+# update_engine. For the main update_engine policy, see
+# external/sepolicy/update_engine.te
+
+# Allow read/write on whole disk. This is needed because the msm8916
+# boot_control HAL modifies the partition table when managing A/B.
+allow update_engine mmc_block_device:blk_file rw_file_perms;