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>
diff --git a/drivers/usb/eth/asix.c b/drivers/usb/eth/asix.c
index 2f116c0..a3bf51a 100644
--- a/drivers/usb/eth/asix.c
+++ b/drivers/usb/eth/asix.c
@@ -419,7 +419,7 @@
 	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;