ixgbe: refactor ixgbe_alloc_queues()

I noticed ring variable was initialized before allocations, and that
memory node management was a bit ugly. We also leak memory in case of
ring allocations error.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>