platform: Uniform struct field name for Numeric SensorValue PDR

The PDR structure has a field for entity instance number.
This commit is making the field name uniform across all the PDR
structures defined because the user APIs can access these
structures using a common template.

Added it as a union for now but later in time we will remove
the union and the non-uniform field name.

Change-Id: I36d4c9ac80ccbd4b539cb2efa02af727be265565
Signed-off-by: Pavithra Barithaya <pavithra.b@ibm.com>
diff --git a/include/libpldm/platform.h b/include/libpldm/platform.h
index 9018dd2..03243b4 100644
--- a/include/libpldm/platform.h
+++ b/include/libpldm/platform.h
@@ -726,7 +726,10 @@
 	uint16_t terminus_handle;
 	uint16_t sensor_id;
 	uint16_t entity_type;
-	uint16_t entity_instance_num;
+	union {
+		uint16_t entity_instance_num;
+		uint16_t entity_instance;
+	};
 	uint16_t container_id;
 	uint8_t sensor_init;
 	bool8_t sensor_auxiliary_names_pdr;