igb: Link IRQs to NAPI instances

igb: Link IRQs to NAPI instances

Link IRQs to NAPI instances via netdev-genl API. This allows users to query
that information via netlink:

|$ ./tools/net/ynl/pyynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
|                               --dump napi-get --json='{"ifindex": 2}'
|[{'defer-hard-irqs': 0,
|  'gro-flush-timeout': 0,
|  'id': 8204,
|  'ifindex': 2,
|  'irq': 127,
|  'irq-suspend-timeout': 0},
| {'defer-hard-irqs': 0,
|  'gro-flush-timeout': 0,
|  'id': 8203,
|  'ifindex': 2,
|  'irq': 126,
|  'irq-suspend-timeout': 0},
| {'defer-hard-irqs': 0,
|  'gro-flush-timeout': 0,
|  'id': 8202,
|  'ifindex': 2,
|  'irq': 125,
|  'irq-suspend-timeout': 0},
| {'defer-hard-irqs': 0,
|  'gro-flush-timeout': 0,
|  'id': 8201,
|  'ifindex': 2,
|  'irq': 124,
|  'irq-suspend-timeout': 0}]
|$ cat /proc/interrupts | grep enp2s0
|123:          0          1 IR-PCI-MSIX-0000:02:00.0   0-edge      enp2s0
|124:          0          7 IR-PCI-MSIX-0000:02:00.0   1-edge      enp2s0-TxRx-0
|125:          0          0 IR-PCI-MSIX-0000:02:00.0   2-edge      enp2s0-TxRx-1
|126:          0          5 IR-PCI-MSIX-0000:02:00.0   3-edge      enp2s0-TxRx-2
|127:          0          0 IR-PCI-MSIX-0000:02:00.0   4-edge      enp2s0-TxRx-3

Reviewed-by: Joe Damato <jdamato@fastly.com>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>