firmware: scmi: fix uninitialized flags

flags in shared memory is not set, this flags is now set to avoid
a notification by server when request is completed

Change-Id: Idf0a73eaf480f671f22b3693deddd9da1bada4cb
Signed-off-by: Michel JAOUEN <michel.jaouen@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/u-boot/+/446887
ACI: CIBUILD <MDG-smet-aci-builds@list.st.com>
Reviewed-by: Patrice CHOTARD <patrice.chotard@foss.st.com>
ACI: CITOOLS <MDG-smet-aci-reviews@list.st.com>
Domain-Review: Patrick DELAUNAY <patrick.delaunay@foss.st.com>

Author: jamike

drivers/firmware/scmi/smt.c

@@ -87,6 +87,7 @@ int scmi_write_msg_to_smt(struct udevice *dev, struct scmi_smt *smt,
 	/* Load message in shared memory */
 	hdr->channel_status &= ~SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE;
 	hdr->length = msg->in_msg_sz + sizeof(hdr->msg_header);
+	hdr->flags = 0;
 	hdr->msg_header = SMT_HEADER_TOKEN(0) |
 			  SMT_HEADER_MESSAGE_TYPE(0) |
 			  SMT_HEADER_PROTOCOL_ID(msg->protocol_id) |