openpower: Add GetPELJSON method

This method returns a PEL in JSON format so it can be returned in
Redfish via an OEM attachment.

It's a method and not a property on the PEL.Entry interface because it
is fairly slow and it would bog down GetManagedObjects calls that don't
care about it.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I6d04cd4e301980f95736c05dd5e5b027d400d49b
diff --git a/yaml/org/open_power/Logging/PEL.interface.yaml b/yaml/org/open_power/Logging/PEL.interface.yaml
index 80fd0b1..a3e39f4 100644
--- a/yaml/org/open_power/Logging/PEL.interface.yaml
+++ b/yaml/org/open_power/Logging/PEL.interface.yaml
@@ -148,6 +148,24 @@
       errors:
           - xyz.openbmc_project.Common.Error.InvalidArgument
 
+    - name: GetPELJSON
+      description: >
+          Returns a string containing the JSON representation
+          of the PEL.
+      parameters:
+          - name: bmcLogId
+            type: uint32
+            description: >
+                The BMC event log id of the PEL to retrieve JSON for
+      returns:
+          - name: json
+            type: string
+            description: >
+                The PEL in JSON format
+      errors:
+          - xyz.openbmc_project.Common.Error.InvalidArgument
+          - xyz.openbmc_project.Common.Error.InternalFailure
+
 enumerations:
     - name: RejectionReason
       description: >