ixgbevf: remove counters for Tx/Rx checksum offload

This patch removes the Tx/Rx counters for checksum offload.

The Tx counter was never updated and the Rx counter is of limited use.
This is in effort to clean up the counters and make them consistent
with the counters shown by ixgbe.

Also this patch removes some members of the adapter structure that were
never used and shuffles others to reduce number of holes.

before:
	/* size: 1568, cachelines: 25, members: 48 */
	/* sum members: 1519, holes: 10, sum holes: 43 */
	/* padding: 6 */
	/* last cacheline: 32 bytes */

after:
	/* size: 1480, cachelines: 24, members: 43 */
	/* sum members: 1479, holes: 1, sum holes: 1 */
	/* last cacheline: 8 bytes */

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>