Add attribute to support slow PCI ref clock on Nimbus DD1

ATTR_DD1_SLOW_PCI_REF_CLOCK can be set to run the PCI ref clock
94MHz in order to enable experimental GEN4 support.

Change-Id: I98a14762986a52e24f8a14027a65468e55bc2254
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/37596
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: NAGENDRA K. GURRAM <nagendra.g@in.ibm.com>
Reviewed-by: Matthew A. Ploetz <maploetz@us.ibm.com>
Reviewed-by: Dean Sanner <dsanner@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/usr/targeting/common/xmltohb/attribute_types.xml

@@ -14735,6 +14735,27 @@ Measured in GB</description>
     </hwpfToHbAttrMap>
 </attribute>
 
+<attribute>
+    <id>DD1_SLOW_PCI_REF_CLOCK</id>
+    <description>
+        Valid only for Nimbus DD1
+        If set (=1), run the PCI Ref clock at 94MHz in order to enable
+          experimental GEN4 support.
+        If not set (=0), run the PCI Ref clock at 100MHz
+    </description>
+    <simpleType>
+        <uint8_t>
+            <default>0</default>
+        </uint8_t>
+    </simpleType>
+    <persistency>non-volatile</persistency>
+    <readable/>
+    <hwpfToHbAttrMap>
+        <id>ATTR_DD1_SLOW_PCI_REF_CLOCK</id>
+        <macro>DIRECT</macro>
+    </hwpfToHbAttrMap>
+</attribute>
+
 <attribute>
     <id>MEMB_DMI_REFCLOCK_RCVR_TERM</id>
     <description>

src/usr/targeting/common/xmltohb/target_types.xml

@@ -606,6 +606,7 @@
     <attribute><id>BMC_FRU_ID</id></attribute>
     <attribute><id>PROC_REFCLOCK_RCVR_TERM</id></attribute>
     <attribute><id>PCI_REFCLOCK_RCVR_TERM</id></attribute>
+    <attribute><id>DD1_SLOW_PCI_REF_CLOCK</id></attribute>
     <attribute><id>MIN_FREQ_MHZ</id></attribute>
     <attribute><id>DPO_MIN_FREQ_PERCENT</id></attribute>
     <attribute><id>FREQ_PROC_REFCLOCK</id></attribute>