In ixgbevf_get_ringparam we could run into a NULL pointer dereference
if the rings were not allocated when we attempted the call.  To prevent
that we can just access the tx/rx_ring_count values instead of attempting
to access the rings to get the count.

This change corrects a memory leak and memory corruption in
ixgbevf_set_ringparam.

The memory leak was due to us not freeing the resources from the ring
before overwriting them.  This change corrects the memory leak by making
certain to call ixgbe_free_tx/rx_resources on the rings prior to freeing
them.

The memory corruption was because we were replacing the rings but not
updating the q_vectors.  It addresses the memory corruption by leaving the
rings in place and instead just copying the contents of the new rings into
the existing rings.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>