firmware: arm_scmi: Fix range check for the maximum number of pending messages

SCMI message headers carry a sequence number and such field is sized to
allow for MSG_TOKEN_MAX distinct numbers; moreover zero is not really an
acceptable maximum number of pending in-flight messages.

Fix accordingly the checks performed on the value exported by transports
in scmi_desc.max_msg

Link: https://lore.kernel.org/r/20210712141833.6628-3-cristian.marussi@arm.comReported-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
[sudeep.holla: updated the patch title and error message]
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/driver.c

@@ -1026,8 +1026,9 @@ static int __scmi_xfer_info_init(struct scmi_info *sinfo,
 	const struct scmi_desc *desc = sinfo->desc;
 
 	/* Pre-allocated messages, no more than what hdr.seq can support */
-	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {
-		dev_err(dev, "Maximum message of %d exceeds supported %ld\n",
+	if (WARN_ON(!desc->max_msg || desc->max_msg > MSG_TOKEN_MAX)) {
+		dev_err(dev,
+			"Invalid maximum messages %d, not in range [1 - %lu]\n",
 			desc->max_msg, MSG_TOKEN_MAX);
 		return -EINVAL;
 	}