net: introduce transparent driver private in ueth_data

Avoid clutter in ueth_data. Individual drivers should not mess
with structures belonging to the core like this.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/include/usb_ether.h b/include/usb_ether.h
index a7fb26b..7c7aecb 100644
--- a/include/usb_ether.h
+++ b/include/usb_ether.h
@@ -50,12 +50,8 @@
 	unsigned char	protocol;		/* .............. */
 	unsigned char	irqinterval;	/* Intervall for IRQ Pipe */
 
-	/* private fields for each driver can go here if needed */
-#ifdef CONFIG_USB_ETHER_SMSC95XX
-	size_t rx_urb_size;  /* maximum USB URB size */
-	u32 mac_cr;  /* MAC control register value */
-	int have_hwaddr;  /* 1 if we have a hardware MAC address */
-#endif
+	/* driver private */
+	void *dev_priv;
 };
 
 /*