net/i40e: fix Rx packet statistics

net/i40e: fix Rx packet statistics

Some packets are discarded by the NIC because they are larger than
the MTU, these packets should be counted as "RX error" instead of
"RX packet", for example:

  pkt1 = Ether()/IP()/Raw('x' * 1400)
  pkt2 = Ether()/IP()/Raw('x' * 1500)

  ---------------- Forward statistics for port 0 -----------------
  RX-packets: 2 RX-dropped: 0 RX-total: 2
  TX-packets: 1 TX-dropped: 0 TX-total: 1
  ----------------------------------------------------------------

  Here the packet pkt2 has been discarded, but still was counted
  by "RX-packets"

The register 'GL_RXERR1' can count above discarded packets.
This patch adds reading and calculation of the 'GL_RXERR1' counter
when reporting DPDK statistics.

Fixes: f4a91c38b4ad ("i40e: add extended stats")
Cc: stable@dpdk.org
Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>