PEL: Point action flags documention to its rules

Add a link from where the PEL action flags are described to the rules on
how the code sets them.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I5d562ff447913f0fd8dd784ea809873917aa696b
diff --git a/extensions/openpower-pels/registry/README.md b/extensions/openpower-pels/registry/README.md
index 51702ca..f1c90f9 100644
--- a/extensions/openpower-pels/registry/README.md
+++ b/extensions/openpower-pels/registry/README.md
@@ -117,7 +117,8 @@
 if not supplied the code will fill them in based on those fields.
 
 In fact, even if supplied here, the code may still modify them to ensure they
-are correct.
+are correct.  The rules used for this are
+[here](../README.md#action-flags-and-event-type-rules).
 
 ```
 "ActionFlags": ["service_action", "report", "call_home"]