base: Define macros for reserved TIDs

Move the definition of `PLDM_TID_RESERVED` from platform.h to base.h as
the value is defined in the base specification (DSP0240). platform.h
already includes base.h so the move is not an API-breaking change.

Further, add the definition for `PLDM_TID_UNASSIGNED`, which is the
other reserved TID value.

Change-Id: I191bee73e091a4b0e83c4bffcee38bff3c88ed96
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1a9dd7..5f094c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,10 @@
 
 ## [Unreleased]
 
+### Added
+
+1. base: Define macros for reserved TIDs
+
 ## [0.8.0] - 2024-05-23
 
 ### Added
diff --git a/include/libpldm/base.h b/include/libpldm/base.h
index 01a0418..562ef58 100644
--- a/include/libpldm/base.h
+++ b/include/libpldm/base.h
@@ -95,6 +95,8 @@
 #define PLDM_MAX_TYPES	       64
 #define PLDM_MAX_CMDS_PER_TYPE 256
 #define PLDM_MAX_TIDS	       256
+#define PLDM_TID_UNASSIGNED    0x00
+#define PLDM_TID_RESERVED      0xff
 
 /* Message payload lengths */
 #define PLDM_GET_COMMANDS_REQ_BYTES 5
diff --git a/include/libpldm/platform.h b/include/libpldm/platform.h
index db28468..ece3ab1 100644
--- a/include/libpldm/platform.h
+++ b/include/libpldm/platform.h
@@ -94,7 +94,6 @@
 	 PLDM_PDR_NUMERIC_EFFECTER_PDR_VARIED_RANGE_FIELD_MIN_LENGTH)
 
 #define PLDM_INVALID_EFFECTER_ID 0xffff
-#define PLDM_TID_RESERVED	 0xff
 
 /* DSP0248 Table1 PLDM monitoring and control data types */
 #define PLDM_STR_UTF_8_MAX_LEN	256