mlxsw: core: Enable devlink reload only on probe

Call devlink enable only during probe time and avoid deadlock
during reload.

Reported-by: Shalom Toledo <shalomt@mellanox.com>
Fixes: a0c76345 ("devlink: disallow reload operation during device cleanup")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Tested-by: Shalom Toledo <shalomt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>