[minigraph] remove number of lanes check for changing speed from 400G…

… to 100G and set speed setting before lane reconfiguration (#15721) (#16054)

src/sonic-config-engine/minigraph.py

@@ -1766,6 +1766,9 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None, hw
         port_default_speed =  port_speeds_default.get(port_name, None)
         port_png_speed = port_speed_png[port_name]
 
+        # set Port Speed before lane update
+        ports.setdefault(port_name, {})['speed'] = port_png_speed
+
         # when the port speed is changes from 400g to 100g/40g
         # update the port lanes, use the first 4 lanes of the 400G port to support 100G/40G port
         if port_default_speed == '400000' and (port_png_speed == '100000' or port_png_speed == '40000'):
@@ -1776,7 +1779,6 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None, hw
             updated_lanes = ",".join(port_lanes[:4])
             ports[port_name]['lanes'] = updated_lanes
 
-        ports.setdefault(port_name, {})['speed'] = port_speed_png[port_name]
 
     for port_name, port in list(ports.items()):
         # get port alias from port_config.ini