Use predefined macro as vendor information (#8361)

#### Why I did it
Use a predefined variable to get vendor information when the swss docker container is created

#### How I did it
Use `{{ sonic_asic_platform }}` instead of `$SONIC_CFGGEN -y /etc/sonic/sonic_version.yml -v asic_type`

#### How to verify it
Manually test.

files/build_templates/docker_image_ctl.j2

@@ -277,9 +277,6 @@ start() {
     {%- endif %}
 
     {%- if docker_container_name == "swss" %}
-    # Obtain the vendor name
-    ASIC_VENDOR=`$SONIC_CFGGEN -y /etc/sonic/sonic_version.yml -v asic_type`
-
     # Generate the asic_table.json and peripheral_table.json
     if [ ! -f /etc/sonic/asic_table.json ] && [ -f /usr/share/sonic/templates/asic_table.j2 ]; then
         sonic-cfggen -d -t /usr/share/sonic/templates/asic_table.j2 > /etc/sonic/asic_table.json
@@ -405,7 +402,7 @@ start() {
 {%- endif %}
 {%- endif %}
 {%- if docker_container_name == "swss" %}
-        -e ASIC_VENDOR=$ASIC_VENDOR \
+        -e ASIC_VENDOR={{ sonic_asic_platform }} \
 {%- endif -%}
 {%- if docker_container_name == "bgp" %}
         -v /etc/sonic/frr/$DEV:/etc/frr:rw \