host: Fix setting conn's peer RPA address in SM
host: Fix setting conn's peer RPA address in SM

Change introduced in previous commit already
stores a peer RPA address in proper field inside
connection structure, so we can update the condition to
use peer_rpa_addr field to check if address was resolved.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble