imx: ventana: assign default ethprime dynamically

Gateworks Ventana boards don't all use IMX6 FEC, so lets define default
ethprime based off the first detected device.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/board/gateworks/gw_ventana/gw_ventana.c b/board/gateworks/gw_ventana/gw_ventana.c
index 303b13a..84d7124 100644
--- a/board/gateworks/gw_ventana/gw_ventana.c
+++ b/board/gateworks/gw_ventana/gw_ventana.c
@@ -413,6 +413,15 @@
 	usb_eth_initialize(bis);
 #endif
 
+	/* default to the first detected enet dev */
+	if (!getenv("ethprime")) {
+		struct eth_device *dev = eth_get_dev_by_index(0);
+		if (dev) {
+			setenv("ethprime", dev->name);
+			printf("set ethprime to %s\n", getenv("ethprime"));
+		}
+	}
+
 	return 0;
 }