uml/net_kern: Call dev_consume_skb_any instead of dev_kfree_skb.

Replace dev_kfree_skb with dev_consume_skb_any in uml_net_start_xmit
as it can be called in hard irq and other contexts.

dev_consume_skb_any is used as uml_net_start_xmit typically
consumes (not drops) packets.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>