i40e: don't add more vectors to num_lan_msix than number of CPUs

This is a solution to avoid adding too many queues to num_lan_msix.
A recent refactor of queue pairs accidentally added all remaining
vectors to the num_lan_msix which can have adverse performance issues,
due to enabling more queues than the number of CPU cores.

This patch removes the old calculation, and replaces it with a simple
algorithm.

1) add queue pairs up to num_online_cpus(), but capped at half of total
   vectors
2) then add alternative features such as flow directory and similar
3) finally, add the remaining vectors back to queue pairs, but capped
   such that the total number of queue pairs does not exceed
   num_online_cpus().

Change-ID: I668abf67d5011a1248866daba8885f4ff00cb8d9
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Harshitha Ramamurthy <harshitha.ramamurthy@intel.com>
Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>