Currently is_assoc_link flag in cdp_peer_setup_info just means first
link peer during MLO connection, but usually assoc_link is the
link which initialize MLO association and it will be the primary_link.
this introduce confusion with another flag is_primary_link.
Change it to 'is_first_link' in cdp_peer_setup_info
Change-Id: I8d14da73e6a3bbc39a4a527d6c0aa5667255e995
CRs-Fixed: 3090270