cm: sepolicy: fix denials for external storage

Change-Id: I784a859671c69370cab0118a88a5fb0190352af9
diff --git a/sepolicy/fsck_untrusted.te b/sepolicy/fsck_untrusted.te
new file mode 100644
index 0000000..5d12f76
--- /dev/null
+++ b/sepolicy/fsck_untrusted.te
@@ -0,0 +1,2 @@
+# External storage
+allow fsck_untrusted self:capability sys_admin;