Overview:
We don't frequently change the msix vectors throughout the life cycle of
the driver. We do so in two functions: ena_probe() and ena_restore().
ena_probe() is only called when the driver is loaded. ena_restore() on the
other hand is called during device reset / resume operations.

We use num_io_queues for calculating and allocating the number of msix
vectors. At ena_probe() this value is equal to max_num_io_queues and thus
this is not an issue, however ena_restore() might be called after the
number of io queues has changed.

A possible bug scenario is as follows:

* Change number of queues from 8 to 4.
  (num_io_queues = 4, max_num_io_queues = 8, msix_vecs = 9,)
* Trigger reset occurs -> ena_restore is called.
  (num_io_queues = 4, max_num_io_queues =8 , msix_vecs = 5)
* Change number of queues from 4 to 6.
  (num_io_queues = 6, max_num_io_queues = 8, msix_vecs = 5)
* The driver will reset due to failure of check_for_rx_interrupt_queue()

Fix:
This can be easily fixed by always using max_num_io_queues to init the
msix_vecs, since this number won't change as opposed to num_io_queues.

Fixes: 4d192660 ("net: ena: multiple queue creation related cleanups")
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>