net/mlx5e: Fix crash moving to switchdev mode when ntuple offload is set

Moving to switchdev mode with ntuple offload on causes the kernel to
crash since fs->arfs is freed during nic profile cleanup flow.

Ntuple offload is not supported in switchdev mode and it is already
unset by mlx5 fix feature ndo in switchdev mode. Verify fs->arfs is
valid before disabling it.

trace:
[] RIP: 0010:_raw_spin_lock_bh+0x17/0x30
[] arfs_del_rules+0x44/0x1a0 [mlx5_core]
[] mlx5e_arfs_disable+0xe/0x20 [mlx5_core]
[] mlx5e_handle_feature+0x3d/0xb0 [mlx5_core]
[] ? __rtnl_unlock+0x25/0x50
[] mlx5e_set_features+0xfe/0x160 [mlx5_core]
[] __netdev_update_features+0x278/0xa50
[] ? netdev_run_todo+0x5e/0x2a0
[] netdev_update_features+0x22/0x70
[] ? _cond_resched+0x15/0x30
[] mlx5e_attach_netdev+0x12a/0x1e0 [mlx5_core]
[] mlx5e_netdev_attach_profile+0xa1/0xc0 [mlx5_core]
[] mlx5e_netdev_change_profile+0x77/0xe0 [mlx5_core]
[] mlx5e_vport_rep_load+0x1ed/0x290 [mlx5_core]
[] mlx5_esw_offloads_rep_load+0x88/0xd0 [mlx5_core]
[] esw_offloads_load_rep.part.38+0x31/0x50 [mlx5_core]
[] esw_offloads_enable+0x6c5/0x710 [mlx5_core]
[] mlx5_eswitch_enable_locked+0x1bb/0x290 [mlx5_core]
[] mlx5_devlink_eswitch_mode_set+0x14f/0x320 [mlx5_core]
[] devlink_nl_cmd_eswitch_set_doit+0x94/0x120
[] genl_family_rcv_msg_doit.isra.17+0x113/0x150
[] genl_family_rcv_msg+0xb7/0x170
[] ? devlink_nl_cmd_port_split_doit+0x100/0x100
[] genl_rcv_msg+0x47/0xa0
[] ? genl_family_rcv_msg+0x170/0x170
[] netlink_rcv_skb+0x4c/0x130
[] genl_rcv+0x24/0x40
[] netlink_unicast+0x19a/0x230
[] netlink_sendmsg+0x204/0x3d0
[] sock_sendmsg+0x50/0x60

Fixes: 90b22b9b

 ("net/mlx5e: Disable Rx ntuple offload for uplink representor")
Signed-off-by: Amir Tzin <amirtz@nvidia.com>
Reviewed-by: Aya Levin <ayal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>