Sepolicy for rw mount point for vendors.

Bug: 64905218
Test: device boots with /mnt/vendor present and selinux label
mnt_vendor_file applied correctly.
Change-Id: Ib34e2859948019d237cf2fe8f71845ef2533ae27
Merged-In: Ib34e2859948019d237cf2fe8f71845ef2533ae27
(cherry picked from commit 210a805b46782a2a49bf5338732cf8c6abaf95de)
diff --git a/private/file_contexts b/private/file_contexts
index 109f219..4e2a765 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -525,3 +525,7 @@
 /mnt/user(/.*)?             u:object_r:mnt_user_file:s0
 /mnt/runtime(/.*)?          u:object_r:storage_file:s0
 /storage(/.*)?              u:object_r:storage_file:s0
+
+#############################
+# mount point for read-write vendor partitions
+/mnt/vendor(/.*)?          u:object_r:mnt_vendor_file:s0