docs: netdev: update maintainer-netdev.rst reference

docs: netdev: update maintainer-netdev.rst reference

Changeset 8df0136376dc ("docs: netdev: move the netdev-FAQ to the process pages")
renamed: Documentation/networking/netdev-FAQ.rst
to: Documentation/process/maintainer-netdev.rst.

Update its cross-reference accordingly.

Fixes: 8df0136376dc ("docs: netdev: move the netdev-FAQ to the process pages")
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/aed0482b3d931bfcfe84f38197526edcbb8fd830.1656234456.git.mchehab@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>