cxgb4vf: recover from failure in cxgb4vf_open()

If the Link Start fails in cxgb4vf_open(), we need to back out any state
that we've built up ...

Signed-off-by: Casey Leedom <leedom@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>