p9_psi_init -- parametrize link speed (half/full)

  Wrapper tested on zzfp033
  Appears to correctly trigger half speed mode from FSP tool feedback
  $ cat /sys/devices/psi_link0/clock
  FSP-2, PSI(0) CLK overwrite: 1  Speed: 166 MHz

Change-Id: Id03e7fd54a3eff8037ac677399472dbd8a89d1a1
Original-Change-Id: I45997c30e71457ceedfcba70550f0e6d98584a1e
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/31497
Dev-Ready: Joseph J. McGill <jmcgill@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: PPE CI <ppe-ci+hostboot@us.ibm.com>
Reviewed-by: Kevin F. Reick <reick@us.ibm.com>
Reviewed-by: Joseph J. McGill <jmcgill@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/55435
CI-Ready: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Tested-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/import/chips/p9/procedures/xml/attribute_info/chip_ec_attributes.xml

@@ -234,4 +234,22 @@
     </chipEcFeature>
   </attribute>
   <!-- ******************************************************************** --> 
+  <attribute>
+    <id>ATTR_CHIP_EC_FEATURE_PSI_HALF_SPEED</id>
+    <targetType>TARGET_TYPE_PROC_CHIP</targetType>
+    <description>
+      Nimbus DD1 only: enable half speed PSI link operation due to relaxed
+      chip timing closure
+    </description>
+    <chipEcFeature>
+      <chip>
+        <name>ENUM_ATTR_NAME_NIMBUS</name>
+        <ec>
+          <value>0x20</value>
+          <test>LESS_THAN</test>
+        </ec>
+      </chip>
+    </chipEcFeature>
+  </attribute>
+  <!-- ******************************************************************** --> 
 </attributes>