libpldm: Add encode API for CancelUpdate request

Update agent send this command to FD/FDP to exit from update mode
even if activation is required to begin operating at the new firmware
level. FD/FDP will transition to IDLE state on CancelUpdate. This
implementation works with DSP0267_1.1.0, DSP0267_1.0.1 and
DSP0267_1.0.0.

Tested: Unit tests passed

Signed-off-by: gokulsanker <gokul.sanker.v.g@intel.com>
Change-Id: Iab9c2f078c216c20c2432ac5ec0438fdae8da27d
diff --git a/libpldm/firmware_update.c b/libpldm/firmware_update.c
index 6714136..53c1387 100644
--- a/libpldm/firmware_update.c
+++ b/libpldm/firmware_update.c
@@ -1483,3 +1483,27 @@
 	*completion_code = msg->payload[0];

 	return PLDM_SUCCESS;

 }

+

+int encode_cancel_update_req(uint8_t instance_id, struct pldm_msg *msg,

+			     size_t payload_length)

+{

+	if (msg == NULL) {

+		return PLDM_ERROR_INVALID_DATA;

+	}

+

+	if (payload_length != PLDM_CANCEL_UPDATE_REQ_BYTES) {

+		return PLDM_ERROR_INVALID_LENGTH;

+	}

+

+	struct pldm_header_info header = {0};

+	header.instance = instance_id;

+	header.msg_type = PLDM_REQUEST;

+	header.pldm_type = PLDM_FWUP;

+	header.command = PLDM_CANCEL_UPDATE;

+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));

+	if (rc) {

+		return rc;

+	}

+

+	return PLDM_SUCCESS;

+}