platform: Stabilise decode_pldm_message_poll_event_data() APIs

See usage example at:
[1] https://gerrit.openbmc.org/c/openbmc/pldm/+/73033/1/platform-mc/event_manager.cpp#126

Change-Id: Ic680a514b224d366cc00fa291f2da45dde77950a
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
diff --git a/src/dsp/platform.c b/src/dsp/platform.c
index 4557d89..f826f3c 100644
--- a/src/dsp/platform.c
+++ b/src/dsp/platform.c
@@ -1902,7 +1902,7 @@
 	return pldm_msgbuf_destroy(buf);
 }
 
-LIBPLDM_ABI_TESTING
+LIBPLDM_ABI_STABLE
 int decode_pldm_message_poll_event_data(
 	const void *event_data, size_t event_data_length,
 	struct pldm_message_poll_event *poll_event)