hwmon: (pmbus/tps53679) Fix build warning

If CONFIG_OF is not enabled, the following build warning is observed.

drivers/hwmon/pmbus/tps53679.c:100:34: warning:
	‘tps53679_of_match’ defined but not used

Marking tps53679_of_match as __maybe_unused fixes the problem.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/tps53679.c

@@ -97,7 +97,7 @@ static const struct i2c_device_id tps53679_id[] = {
 
 MODULE_DEVICE_TABLE(i2c, tps53679_id);
 
-static const struct of_device_id tps53679_of_match[] = {
+static const struct of_device_id __maybe_unused tps53679_of_match[] = {
 	{.compatible = "ti,tps53679"},
 	{}
 };