greybus: hd: fix cport-count check

Fix off-by-one error when checking the number of cports a host-device
supports.

The CPORT_ID_MAX is the largest valid cport id so the maximum number of
cports a host-device can use is CPORT_ID_MAX + 1.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/hd.c

@@ -49,7 +49,7 @@ struct gb_host_device *gb_hd_create(struct gb_hd_driver *driver,
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (num_cports == 0 || num_cports > CPORT_ID_MAX) {
+	if (num_cports == 0 || num_cports > CPORT_ID_MAX + 1) {
 		dev_err(parent, "Invalid number of CPorts: %zu\n", num_cports);
 		return ERR_PTR(-EINVAL);
 	}