KASan reported use-after-free for the hwmon structure. So fix this by
using devm_kzalloc and let the core take care about freeing the memory
during device dettach.
Reported-by: Ido Schimmel <idosch@mellanox.com>
Fixes: 89309da3 ("mlxsw: core: Implement temperature hwmon interface")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>