[multi-Asic] Add support for multi-asic to swssloglevel (#5316)

* Support for multi-asic platform for swssloglevel command

admin@str-acs-1:~$ swssloglevel 
Usage: /usr/bin/swssloglevel -n [0 to 3] [OPTION]... 

* Update to use the env file to get the PLATFORM string.

dockers/docker-orchagent/base_image_files/swssloglevel

@@ -1,10 +1,44 @@
 #!/bin/bash
 
+# read SONiC immutable variables
+[ -f /etc/sonic/sonic-environment ] && . /etc/sonic/sonic-environment
+
+function help()
+{
+    echo -e "Usage: $0 -n [0 to $(($NUM_ASIC-1))] [OPTION]... " 1>&2; exit 1;
+}
+
 DOCKER_EXEC_FLAGS="i"
 
 # Determine whether stdout is on a terminal
 if [ -t 1 ] ; then
     DOCKER_EXEC_FLAGS+="t"
 fi
 
-docker exec -$DOCKER_EXEC_FLAGS swss swssloglevel "$@"
+DEV=""
+PLATFORM=${PLATFORM:-`sonic-cfggen -H -v DEVICE_METADATA.localhost.platform`}
+
+# Parse the device specific asic conf file, if it exists
+ASIC_CONF=/usr/share/sonic/device/$PLATFORM/asic.conf
+[ -f $ASIC_CONF ] && . $ASIC_CONF
+
+if [[ ($NUM_ASIC -gt 1) ]]; then
+    while getopts ":n:h:" opt; do
+        case "${opt}" in
+            h) help
+               ;;
+            n) DEV=${OPTARG}
+               [ $DEV -lt $NUM_ASIC -a  $DEV -ge 0 ] || help
+               ;;
+        esac
+    done
+
+    if [ -z "${DEV}" ]; then
+        help
+    fi
+
+    # Skip the arguments -n <inst> while passing to docker command
+    shift 2
+fi
+
+docker exec -$DOCKER_EXEC_FLAGS swss$DEV swssloglevel "$@"