thermal: int3403_thermal: Fix NULL pointer deref on module load / probe

Starting with kernel 4.17 thermal_cooling_device_register() will call the
get_max_state() op during register.

Since we deref priv->priv in int3403_get_max_state() this means we must
set priv->priv before calling thermal_cooling_device_register().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>