3c59x: Fix resource leaks in vortex_open

When vortex_up is failed, the skb buffers allocated by __netdev_alloc_skb
in vortex_open are not released, which may cause resource leaks.
This bug has been submitted before.
This patch modifies the error handling code to fix it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>