nfp: allocate irqs in lower driver

PF services multiple ports using single PCI device therefore
IRQs can no longer be allocated in the netdev code.  Lower
portion of the driver has to allocate the IRQs and hand them
out to ports.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>