platform: Stabilize get event receiver API

Usage of the get event receiver API is demonstrated here:

https://gerrit.openbmc.org/c/openbmc/pldm/+/78997

Change-Id: I63e168bba4db7c908bebf29edb1248c20163d993
Signed-off-by: Roger G. Coscojuela <roger.gili-coscojuela@sipearl.com>
diff --git a/src/dsp/platform.c b/src/dsp/platform.c
index 21ada82..693727e 100644
--- a/src/dsp/platform.c
+++ b/src/dsp/platform.c
@@ -2561,7 +2561,7 @@
 	return pldm_msgbuf_complete_used(buf, *payload_length, payload_length);
 }
 
-LIBPLDM_ABI_TESTING
+LIBPLDM_ABI_STABLE
 int decode_get_event_receiver_resp(const struct pldm_msg *msg,
 				   size_t payload_length,
 				   struct pldm_get_event_receiver_resp *resp)