drivers/usb/eth/asix.c: Fix build warning

Fix:
asix.c: In function 'asix_eth_get_info':
asix.c:629:12: warning: assignment from incompatible pointer type

Signed-off-by: Anatolij Gustschin <agust@denx.de>

drivers/usb/eth/asix.c

@@ -419,7 +419,7 @@ out_err:
 	return -1;
 }
 
-static int asix_send(struct eth_device *eth, volatile void *packet, int length)
+static int asix_send(struct eth_device *eth, void *packet, int length)
 {
 	struct ueth_data *dev = (struct ueth_data *)eth->priv;
 	int err;