platform/chrome: cros_ec_proto: Avoid -Wflex-array-member-not-at-end warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warnings:

drivers/platform/chrome/cros_ec_proto.c:143:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/platform/chrome/cros_ec_proto.c:761:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Link: https://lore.kernel.org/r/Z-adX1BB30dcSJ7x@kspp
Signed-off-by: Tzung-Bi Shih <[e-mail]>

drivers/platform/chrome/cros_ec_proto.c

···
 
 static int cros_ec_wait_until_complete(struct cros_ec_device *ec_dev, uint32_t *result)
 {
-	struct {
-		struct cros_ec_command msg;
-		struct ec_response_get_comms_status status;
-	} __packed buf;
-	struct cros_ec_command *msg = &buf.msg;
-	struct ec_response_get_comms_status *status = &buf.status;
+	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
+			sizeof(struct ec_response_get_comms_status));
+	struct ec_response_get_comms_status *status =
+			(struct ec_response_get_comms_status *)msg->data;
 	int ret = 0, i;
 
 	msg->version = 0;
···
 
 static int get_next_event(struct cros_ec_device *ec_dev)
 {
-	struct {
-		struct cros_ec_command msg;
-		struct ec_response_get_next_event_v3 event;
-	} __packed buf;
-	struct cros_ec_command *msg = &buf.msg;
-	struct ec_response_get_next_event_v3 *event = &buf.event;
+	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
+			sizeof(struct ec_response_get_next_event_v3));
+	struct ec_response_get_next_event_v3 *event =
+			(struct ec_response_get_next_event_v3 *)msg->data;
 	int cmd_version = ec_dev->mkbp_event_supported - 1;
 	u32 size;
 
-	memset(msg, 0, sizeof(*msg));
 	if (ec_dev->suspended) {
 		dev_dbg(ec_dev->dev, "Device suspended.\n");
 		return -EHOSTDOWN;