i40e: Change firmware workaround

Remove a workaround that is no longer necessary and implement
a better understanding of what firmware is returning in the MSI-X
vector count.  This makes it so that the driver ends up with the
right amount of queues when using all available MSI-X vectors.

Change-ID: I34e60cc71dcfb1b5412f37df956fedcc49ade187
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>