[YANG MODEL] Fix breakout validation failed

- Missing 'ipv6_use_link_local_only' key
- Remove the restriction about no default gateway in the static management IP

src/sonic-yang-models/yang-models/sonic-interface.yang

@@ -67,6 +67,14 @@ module sonic-interface {
                                         default "0";
 				}
 
+				leaf ipv6_use_link_local_only {
+					description "Enable/disable IPv6 link-local";
+					type enumeration {
+						enum enable;
+						enum disable;
+					}
+				}
+
 				leaf mpls {
 					description "Enable/disable MPLS routing for the interface";
 					type enumeration {

src/sonic-yang-models/yang-models/sonic-mgmt_interface.yang

@@ -41,12 +41,12 @@ module sonic-mgmt_interface {
                 }
 
                 leaf ip_prefix {
-                    must "(contains(current(), ':') and contains(../gwaddr, ':')) or (contains(current(), '.') and contains(../gwaddr, '.'))";
+                    must "(contains(current(), ':')) or (contains(current(), '.'))";
                     type stypes:sonic-ip-prefix;
                 }
 
                 leaf gwaddr {
-                    must "(contains(current(), ':') and contains(../ip_prefix, ':')) or (contains(current(), '.') and contains(../ip_prefix, '.'))"; 
+                    must "(contains(current(), ':') and contains(../ip_prefix, ':')) or (contains(current(), '.') and contains(../ip_prefix, '.'))";
                     type inet:ip-address;
                 }
 
@@ -57,11 +57,11 @@ module sonic-mgmt_interface {
                     }
 
                     description
-                        "This configuration allows addtional routes to be added to default VRF table 
+                        "This configuration allows addtional routes to be added to default VRF table
                          or mgmt VRF table, based on if Management VRF is configured.
                          Details can be found in interfaces.j2.";
                 }
- 
+
             } /* end of list MGMT_INTERFACE_IPADDR_LIST */
 
         } /* end of container MGMT_INTERFACE */

src/sonic-yang-models/yang-models/sonic-vlan.yang

@@ -106,6 +106,14 @@ module sonic-vlan {
                     description "Packet action when a packet ingress and gets routed on the same IP interface";
                     type stypes:loopback_action;
                 }
+
+				leaf ipv6_use_link_local_only {
+					description "Enable/disable IPv6 link-local";
+					type enumeration {
+						enum enable;
+						enum disable;
+					}
+				}
 			}
 			/* end of VLAN_INTERFACE_LIST */
 
@@ -163,7 +171,7 @@ module sonic-vlan {
 			list VLAN_LIST {
 
 				key "name";
-        
+
 				leaf name {
 					type string {
 						pattern 'Vlan([0-9]{1,3}|[1-3][0-9]{3}|[4][0][0-8][0-9]|[4][0][9][0-4])';