support for FFDC-only isolation nodes in chip data

Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
Change-Id: Ib457329d31a9f01eb6992e57b11d84c06a63e6e7
diff --git a/xml/node.xsd b/xml/node.xsd
index 5edcb32..2bbe4ec 100644
--- a/xml/node.xsd
+++ b/xml/node.xsd
@@ -17,7 +17,7 @@
             <xsd:element name="capture_group" type="capture_group" minOccurs="0"
                          maxOccurs="255"/>
             <xsd:element name="rule" type="rule" minOccurs="0" maxOccurs="255"/>
-            <xsd:element name="bit"  type="bit"  minOccurs="1" maxOccurs="255"/>
+            <xsd:element name="bit"  type="bit"  minOccurs="0" maxOccurs="255"/>
         </xsd:sequence>
 
         <xsd:attribute name="name"     type="name_type"     use="required"/>