PEL: Add altitude PEL registry entries

These will only be used on systems that use PELs and have the virtual
altitude sensor. The errors come from the sensor-monitor app.

Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>
Change-Id: I5fec3ec86a084f8c62f52194f2826c0565be32eb
diff --git a/extensions/openpower-pels/registry/schema/schema.json b/extensions/openpower-pels/registry/schema/schema.json
index 48397a9..fe42ff1 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", "air_mover", "pgood_part", "usb_pgood", "ambient_temp", "ambient_temp_back", "ambient_perf_loss", "ac_module", "fan_cable", "cable_continued"]
+            "enum": ["service_docs", "pwrsply", "air_mover", "pgood_part", "usb_pgood", "ambient_temp", "ambient_temp_back", "ambient_perf_loss", "ac_module", "fan_cable", "cable_continued", "altitude"]
         },
 
         "symbolicFRUTrusted":