e1000: switch to napi_consume_skb()

e1000: switch to napi_consume_skb()

In order to take the best from per-cpu NAPI skbuff_head caches and
CPU cycles, let's switch from dev_kfree_skb_any(), which passes skb
back to the mm layer, to napi_consume_skb(), which feeds those
caches on non-zero budget instead (falls back to the former on 0).
Do the replacement in e1000_unmap_and_free_tx_resource(). There are
4 call sites of this function throughout the driver:
 * e1000_clean_tx_ring(). Slowpath, process context, cleans the
   whole Tx ring on ifdown. Use budget of 0 here;
 * e1000_tx_map(). Hotpath, net Tx softirq, unmaps the buffers in
   case of error. Use 0 as well;
 * e1000_clean_tx_irq(). Hotpath, NAPI Tx completion polling cycle.
   As the driver doesn't count completed Tx entries towards the NAPI
   budget, just use the poll budget of 64 to utilize caches.

Apart from being a preparation for switching to napi_build_skb(),
this is useful on its own as well, as napi_consume_skb() flushes
skb caches by batches of 32 instead of one-at-a-time.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Tony Brelinski <tony.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>