cxgb4: move the choice of interrupt type before net_device registration

We need to settle on the kind of interrupts we'll be using, a choice that
also impacts the number of queues, before registering and making visible
the net_devices.  Move the relevant code up a bit.

Signed-off-by: Dimitris Michailidis <dm@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>