platform: Uniform struct field name for FRU Record Set PDR

The PDR structure has a field for entity instance number.
This commit is making the field 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: Ib9da47d0b354a6fb67f95ae3c84791dad6daec98
Signed-off-by: Pavithra Barithaya <pavithra.b@ibm.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 033528a..4417982 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -54,6 +54,10 @@
    pldm_state_set_operational_fault_status_values members should move to
    equivalent pldm_state_set_operational_stress_status_values members if needed.
 
+2. platform: Struct field name in fru_record_set PDR
+
+   References to entity_instance_num should be changed to entity_instance
+
 ## [0.4.0] - 2023-07-14
 
 ### Added
diff --git a/include/libpldm/platform.h b/include/libpldm/platform.h
index 26d47c5..9018dd2 100644
--- a/include/libpldm/platform.h
+++ b/include/libpldm/platform.h
@@ -515,7 +515,10 @@
 	uint16_t terminus_handle;
 	uint16_t fru_rsi;
 	uint16_t entity_type;
-	uint16_t entity_instance_num;
+	union {
+		uint16_t entity_instance_num;
+		uint16_t entity_instance;
+	};
 	uint16_t container_id;
 } __attribute__((packed));