ixgbe: Refactor set_num_queues() and cache_ring_register()

The current code to determine the number of queues the device will want
on driver initialization is ugly and difficult to maintain.  It also
doesn't allow for easy expansion for future features or future hardware.
This patch refactors these routines, and make them easier to deal with.

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>