sepolicy_vndr: legacy: Allow using logdump partition as metadata

* sdm845 and sdm710 didn't have a metadata partition, but we can repurpose logdump which is a 64MB partition used to store Android logcats

Change-Id: I826571d4e31f2a3f03c1d3e6a0daab262a4ccd6b
(cherry picked from commit 8a5eeb6a2bfb3f1a7232199d32c1e3c2bbc0ef55)