net: eth-uclass: add function eth_start_udev()

Add a function to start a given network device, and update eth_init()
to use it.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/include/net-common.h b/include/net-common.h
index 543f528..6bc7665 100644
--- a/include/net-common.h
+++ b/include/net-common.h
@@ -192,6 +192,7 @@
 int usb_ether_init(void);
 
 int eth_init(void);			/* Initialize the device */
+int eth_start_udev(struct udevice *dev); /* ->start() if not already running */
 int eth_send(void *packet, int length);	   /* Send a packet */
 #if defined(CONFIG_API) || defined(CONFIG_EFI_LOADER)
 int eth_receive(void *packet, int length); /* Receive a packet*/