use 'LZ' segment for 3d sg_link

Author: soheilshahrouz

vtr_flow/arch/multi_die/stratixiv_3d/3d_SB_inter_die_stratixiv_arch.timing.xml

@@ -48344,7 +48344,7 @@
           <!-- Link going up one layer, using the 'seg4_inter_die_driver' multiplexer to gather connections from the bottom layer and using the LZ node/wire to move up one layer -->
           <sg_link name="L_UP" z_offset="1" x_offset="0" y_offset="0" mux="seg4_inter_die_driver" seg_type="LZ"/>
           <!-- Link going down one layer, using the 'seg4_inter_die_driver' multiplexer to gather connections from the top layer and using the LZ node/wire to down up one layer -->
-          <sg_link name="L_DOWN" z_offset="-1" mux="seg4_inter_die_driver" seg_type="L4"/>
+          <sg_link name="L_DOWN" z_offset="-1" mux="seg4_inter_die_driver" seg_type="LZ"/>
         </sg_link_list>
 
         <!-- Instantiate 6 'L_UP' and 6 'L_DOWN' sg_links per switchblock location everywhere on the device -->