PEL: Add BMC code maintenance procedure

Maintenance procedures are part of the PEL callout section.  This
procedure is used to indicate the problem is due to code (a bug).

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I57c751107dc8caf2dc5406f7ecd58d1b30c635ee
diff --git a/extensions/openpower-pels/registry/schema/schema.json b/extensions/openpower-pels/registry/schema/schema.json
index b3a7df6..37d0bb2 100644
--- a/extensions/openpower-pels/registry/schema/schema.json
+++ b/extensions/openpower-pels/registry/schema/schema.json
@@ -451,7 +451,7 @@
         {
             "description": "The maintenance procedure callout.",
             "type": "string",
-            "enum": ["no_vpd_for_fru"]
+            "enum": ["no_vpd_for_fru", "bmc_code"]
         },
 
         "calloutList":