ixgbe: Fix 82598 MSI-X allocation on systems with more than 8 CPU cores

MSI-X allocation broke after the 82599 merge on systems with more than 8
CPU cores.  82598 drops back into MSI mode, which isn't sufficient to run
full, efficient 10G line rate.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>