Documentation: net-sysfs: describe missing statistics

[ Upstream commit e528afb72a481977456bb18345d4e7f6b85fa7b1 ]

Sync the ABI description with the interface statistics that are currently
available through sysfs.

CC: Jarod Wilson <jarod@redhat.com>
CC: Jonathan Corbet <corbet@lwn.net>
CC: linux-doc@vger.kernel.org
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 5b3fbd61b9d1 ("net: sysfs: Fix /sys/class/net/<iface> path for statistics")
Signed-off-by: Sasha Levin <sashal@kernel.org>