hwmon: (lm63) Fix build warning

The following build warning is seen if CONFIG_OF is disabled.

drivers/hwmon/lm63.c:1156:34: warning:
	‘lm63_of_match’ defined but not used

Mark lm63_of_match as __maybe_unused to fix the problem.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/lm63.c

@@ -1153,7 +1153,7 @@ static const struct i2c_device_id lm63_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, lm63_id);
 
-static const struct of_device_id lm63_of_match[] = {
+static const struct of_device_id __maybe_unused lm63_of_match[] = {
 	{
 		.compatible = "national,lm63",
 		.data = (void *)lm63