neighbour: delete neigh_lookup_nodev as not used

commit 76b9bf965c98c9b53ef7420b3b11438dbd764f92 upstream.

neigh_lookup_nodev isn't used in the kernel after removal
of DECnet. So let's remove it.

Fixes: 1202cdd66531 ("Remove DECnet support from kernel")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/eb5656200d7964b2d177a36b77efa3c597d6d72d.1678267343.git.leonro@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>