greybus: fix error message on parse of cport descriptor size

Fix a simple cut and paste error that was reporting a serial
number header size error rather than a cport descriptor size
error.
Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/core.c

@@ -303,7 +303,7 @@ static int create_cport(struct greybus_module *gmod,
 
 	if (desc_size != sizeof(*cport)) {
 		dev_err(gmod->dev.parent,
-			"invalid serial number header size %zu\n", desc_size);
+			"invalid cport descriptor size %zu\n", desc_size);
 		return -EINVAL;
 	}