enic: bug fix: don't set netdev->name too early

Bug fix: don't set netdev->name early before netdev registration.  Setting
netdev->name early with dev_alloc_name() would occasionally cause netdev
registration to fail returning error that device was already registered.
Since we're using netdev->name to name MSI-X vectors, we now need to
move the request_irq after netdev registartion, so move it to ->open.

Signed-off-by: Scott Feldman <scofeldm@cisco.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>