Macsec fix for portchannel workaround only for Broadcom dnx platforms (sonic-net#10732)

What I did:
macsec workaround for portchannel as define here sonic-net/sonic-swss#2286 applies only to dnx platforms.

This workaround causes failure of macsec bgp protocol testcase on platforms that does not need this workaround.

How I verify:

Test case passes after this change.

Author: abdosi

tests/macsec/macsec_config_helper.py

@@ -88,14 +88,17 @@ def enable_macsec_port(host, port, profile_name):
         return
 
     pc = find_portchannel_from_member(port, get_portchannel(host))
-    if pc:
+
+    dnx_platform = host.facts.get("platform_asic") == 'broadcom-dnx'
+
+    if dnx_platform and pc:
         host.command("sudo config portchannel {} member del {} {}".format(getns_prefix(host, port), pc["name"], port))
         time.sleep(2)
 
     cmd = "sonic-db-cli {} CONFIG_DB HSET 'PORT|{}' 'macsec' '{}'".format(getns_prefix(host, port), port, profile_name)
     host.command(cmd)
 
-    if pc:
+    if dnx_platform and pc:
         time.sleep(2)
         host.command("sudo config portchannel {} member add {} {}".format(getns_prefix(host, port), pc["name"], port))
 
@@ -110,14 +113,16 @@ def disable_macsec_port(host, port):
         return
 
     pc = find_portchannel_from_member(port, get_portchannel(host))
-    if pc:
+    dnx_platform = host.facts.get("platform_asic") == 'broadcom-dnx'
+
+    if dnx_platform and pc:
         host.command("sudo config portchannel {} member del {} {}".format(getns_prefix(host, port), pc["name"], port))
         time.sleep(2)
 
     cmd = "sonic-db-cli {} CONFIG_DB HDEL 'PORT|{}' 'macsec'".format(getns_prefix(host, port), port)
     host.command(cmd)
 
-    if pc:
+    if dnx_platform and pc:
         time.sleep(2)
         host.command("sudo config portchannel {} member add {} {}".format(getns_prefix(host, port), pc["name"], port))