Remove keyref - though ideal, complexity across files & allowance of fabric_idx constant make it difficult to have this in XSD

Author: gmarcosb

src/app/zap-templates/zcl/zcl.xsd

@@ -153,10 +153,6 @@ This schema describes the format of the XML files, that describe the ZCL specifi
       <xs:selector xpath="./struct|enum" />
       <xs:field xpath="@name" />
     </xs:unique>
-    <xs:keyref name="attributeEntryTypeStructRef" refer="structNameKey">
-      <xs:selector xpath="./cluster/attribute" />
-      <xs:field xpath="@entryType" />
-    </xs:keyref>
   </xs:element>
   <xs:element name="deviceType">
     <xs:complexType>