Allow read access in /persist again

Since Android 10 /persist is being labelled mnt_vendor_file instead of
persist_file and we need read access to a file in /persist so adjust the
sepolicy accordingly.

Issue: FP2A10-79
Issue: FP2A10-85
Change-Id: Ib1aca7381f4d6ecbc42ef69c5ad57526964d638f
1 file changed