bpf, docs: Use internal linking for link to netdev subsystem doc

Commit d56b0c46 ("bpf, docs: Fix link to netdev-FAQ target")
attempts to fix linking problem to undefined "netdev-FAQ" label
introduced in 287f4fa9 ("docs: Update references to netdev-FAQ")
by changing internal cross reference to netdev subsystem documentation
(Documentation/process/maintainer-netdev.rst) to external one at
docs.kernel.org. However, the linking problem is still not
resolved, as the generated link points to non-existent netdev-FAQ
section of the external doc, which when clicked, will instead going
to the top of the doc.

Revert back to internal linking by simply mention the doc path while
massaging the leading text to the link, since the netdev subsystem
doc contains no FAQs but rather general information about the subsystem.

Fixes: d56b0c46 ("bpf, docs: Fix link to netdev-FAQ target")
Fixes: 287f4fa9 ("docs: Update references to netdev-FAQ")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230314074449.23620-1-bagasdotme@gmail.com