ixgbe: Reorder the ring to q_vector mapping to improve performance

ixgbe: Reorder the ring to q_vector mapping to improve performance

This change reorders the mapping of rings to q_vectors in the case that the
number of rings exceeds the number of q_vectors.  Previously we would
allocate the first R/N queues to the first q_vector where R is the number
of rings and N is the number of q_vectors.  Instead of doing this we can do
a better job of interleaving the rings to the CPUs by assigning every Nth
ring to the q_vector.

The below tables illustrate this change for the R = 16 N = 4 case.
          Before patch  After patch
q_vector:  0  1  2  3    0  1  2  3
Rings:     0  4  8 12    0  1  2  3
           1  5  9 13    4  5  6  7
           3  6 10 14    8  9 10 11
           4  7 11 15   12 13 14 15

This should improve the performance for both DCB or ATR when the number of
rings exceeds the number of q_vectors allocated by the adapter.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>