[swss] Adding conditional for bgp when on multi ASIC platform (#11691)

bgp should be a per-asic service, and runs for each namespace on
multi-asic platforms. However, putting bgp in MULTI_INST_DEPENDENT
causes swss to be restarted as well as bgp. this is causing issues after #11000

Issue: #11653

This fix:

removes bgp from dependents list
adds a conditional that either adds bgp, or bgp@$DEV to separate
between single and multi-asic platforms

files/scripts/swss.sh

@@ -9,7 +9,9 @@ LOCKFILE="/tmp/swss-syncd-lock$DEV"
 NAMESPACE_PREFIX="asic"
 ETC_SONIC_PATH="/etc/sonic/"
 
-DEPENDENT="radv bgp"
+# DEPENDENT initially contains namespace independent services
+# namespace specific services are added later in this script.
+DEPENDENT="radv"
 MULTI_INST_DEPENDENT="teamd"
 
 . /usr/local/bin/asic_status.sh
@@ -309,9 +311,11 @@ function check_peer_gbsyncd()
 if [ "$DEV" ]; then
     NET_NS="$NAMESPACE_PREFIX$DEV" #name of the network namespace
     SONIC_DB_CLI="sonic-db-cli -n $NET_NS"
+    DEPENDENT+=" bgp@${DEV}"
 else
     NET_NS=""
     SONIC_DB_CLI="sonic-db-cli"
+    DEPENDENT+=" bgp"
 fi
 
 check_peer_gbsyncd