iio.h: Document URI for IPv6 addresses with interface name

Add information about how to construct a URI with a IPv6 address that
contains the interface name. This pattern is used with link-local
addresses.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>

iio.h

@@ -475,6 +475,8 @@ __api __check_ret struct iio_context * iio_create_network_context(const char *ho
  * - ip:192.168.1.119:40000 Port 40000
  * - ip:2601:190:400:da:47b3:55ab:3914:bff1 Default Port
  * - ip:[2601:190:400:da:9a90:96ff:feb5:acaa]:40000 Port 40000
+ * - ip:fe80::f14d:3728:501e:1f94%eth0 Link-local through eth0, default port
+ * - ip:[fe80::f14d:3728:501e:1f94%eth0]:40000 Link-local through eth0, port 40000
  * - USB backend, "usb:"\n When more than one usb device is attached, requires
  * bus, address, and interface parts separated with a dot. For example
  * <i>"usb:3.32.5"</i>. Where there is only one USB device attached, the shorthand