net/mlx5e: IPoIB, Fix access to invalid memory address

net/mlx5e: IPoIB, Fix access to invalid memory address

[ Upstream commit 38e8a5c040d3ec99a8351c688dcdf0f549611565 ]

When cleaning rdma netdevice we need to save the mdev pointer
because priv is released when we release netdev.

This bug was found using the kernel address sanitizer (KASAN).
use-after-free in mlx5_rdma_netdev_free+0xe3/0x100 [mlx5_core]

Fixes: 48935bbb7ae8 ("net/mlx5e: IPoIB, Add netdevice profile skeleton")
Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>