scsi: target: fix unsigned comparision with less than zero

Currently an error return is being assigned to an unsigned size_t varianle
and then checked if the result is less than zero which will always be
false.  Fix this by making ret ssize_t rather than a size_t.

Fixes: 0322913c ("scsi: target: Add device product id and revision configfs attributes")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_configfs.c

@@ -1267,7 +1267,8 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
 	char *stripped = NULL;
-	size_t len, ret;
+	size_t len;
+	ssize_t ret;
 
 	len = strlcpy(buf, page, sizeof(buf));
 	if (len < sizeof(buf)) {
@@ -1322,7 +1323,8 @@ static ssize_t target_wwn_product_id_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_MODEL_LEN + 2];
 	char *stripped = NULL;
-	size_t len, ret;
+	size_t len;
+	ssize_t ret;
 
 	len = strlcpy(buf, page, sizeof(buf));
 	if (len < sizeof(buf)) {
@@ -1377,7 +1379,8 @@ static ssize_t target_wwn_revision_store(struct config_item *item,
 	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
 	unsigned char buf[INQUIRY_REVISION_LEN + 2];
 	char *stripped = NULL;
-	size_t len, ret;
+	size_t len;
+	ssize_t ret;
 
 	len = strlcpy(buf, page, sizeof(buf));
 	if (len < sizeof(buf)) {