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>