PEL: Add fan missing PEL registry entry

This error is created by phosphor-fan-presence-tach after a fan has been
unplugged for a certain amount of time.

It calls out the backplane as low.  In the future, this may be dependent
on system/chassis type but that property is not available on D-bus yet.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I28738cb81d41f2f804f942d4a44f1aa125231b5e
diff --git a/extensions/openpower-pels/registry/schema/schema.json b/extensions/openpower-pels/registry/schema/schema.json
index 8f83c95..50c2d2d 100644
--- a/extensions/openpower-pels/registry/schema/schema.json
+++ b/extensions/openpower-pels/registry/schema/schema.json
@@ -438,7 +438,7 @@
         {
             "description": "The symbolic FRU callout.",
             "type": "string",
-            "enum": ["service_docs", "pwrsply"]
+            "enum": ["service_docs", "pwrsply", "air_mover"]
         },
 
         "symbolicFRUTrusted":