i40evf: store ring size in ring structs

Keep the descriptor ring size in the actual ring structs instead of in
the adapter struct. This enables us to use common tx and rx code with
the i40e PF driver.

Also update copyrights.

Change-ID: I2861e599b2b4c76441c062ea14400f4750f54d0e
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>