mlxsw: spectrum_nve: Do not take reference when looking up netdevice

mlxsw_sp_nve_fid_disable() is always called under RTNL. It is therefore
safe to call __dev_get_by_index() to get the netdevice pointer without
bumping the reference count, because we can be sure the netdevice is not
going away. That then obviates the need to put the netdevice later in the
function.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/341d1046f89d8d839d9d00e4a3d58cdc351e9397.1690471774.git.petrm@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>