hwmon: (tmp421) ignore non-channel related DT nodes

In case the DT contains some nodes not describing the input channels,
ignore them instead of exiting with error.

Signed-off-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
Link: https://lore.kernel.org/r/8e9e332b18dc2cf545f8e8255157e408d356f916.1634206677.git.krzysztof.adamski@nokia.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>