net: sysfs: Fix /sys/class/net/<iface> path

The documentation is pointing to the wrong path for the interface.
Documentation is pointing to /sys/class/<iface>, instead of
/sys/class/net/<iface>.

Fix it by adding the `net/` directory before the interface.

Fixes: 1a02ef76

 ("net: sysfs: add documentation entries for /sys/class/<iface>/queues")
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240131102150.728960-2-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>