nfp: always unmask aux interrupts at init

The link state and exception interrupts may be masked when we probe.
The firmware should in theory prevent sending (and automasking) those
interrupts if the device is disabled, but if my reading of the FW code
is correct there are firmwares out there with race conditions in this
area.  The interrupt may also be masked if previous driver which used
the device was malfunctioning and we didn't load the FW (there is no
other good way to comprehensively reset the PF).

Note that FW unmasks the data interrupts by itself when vNIC is
enabled, such helpful operation is not performed for LSC/EXN interrupts.

Always unmask the auxiliary interrupts after request_irq().  On the
remove path add missing PCI write flush before free_irq().

Fixes: 4c352362

 ("net: add driver for Netronome NFP4000/NFP6000 NIC VFs")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>