poweroffalarm: Fix denial to vendor_iop_prop

Add policy to fix denial to vendor_iop_prop:

avc: denied { read } for pid=2196 comm="i.poweroffalarm"
name="u:object_r:vendor_iop_prop:s0" dev="tmpfs" ino=25694
scontext=u:r:poweroffalarm_app:s0 tcontext=u:object_r:
vendor_iop_prop:s0 tclass=file permissive=0

CRs-Fixed: 2284871
Change-Id: I383b93c01e5af0451a276231c1a2c0fe9aecbcd4