thermal: of: Make thermal_zone_of_sensor_register return -ENODEV if a sensor OF node is missing

When devm_thermal_zone_of_sensor_register() is called from
hwmon_thermal_add_sensor() it is possible that the relevant sensor is
missing an OF node. In this case thermal_zone_of_sensor_register() returns
-EINVAL which causes hwmon_thermal_add_sensor() to fail as well. This patch
changes relevant return code of thermal_zone_of_sensor_register() to
-ENODEV, which is tolerated by hwmon_thermal_add_sensor().

Here is a particular case of such behaviour: the Marvell ethernet PHYs
driver registers hwmon device for the built-in temperature sensor (see
drivers/net/phy/marvell.c). Since the sensor doesn't have associated OF
node devm_hwmon_device_register() returns error which ultimately causes
failure of the PHY driver's probe function.

Signed-off-by: Peter Mamonov <pmamonov@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20190827143952.19591-1-pmamonov@gmail.com