leds: tca6507: fix warning triggered by fwnode conversion.

Robot complains about:

All warnings (new ones prefixed by >>):

>> drivers/leds/leds-tca6507.c:750:34: warning: unused variable
   'of_tca6507_leds_match'    [-Wunused-const-variable]
      static const struct of_device_id of_tca6507_leds_match[] = {

Fix it.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/leds-tca6507.c

@@ -747,7 +747,7 @@ tca6507_led_dt_init(struct i2c_client *client)
 	return pdata;
 }
 
-static const struct of_device_id of_tca6507_leds_match[] = {
+static const struct of_device_id __maybe_unused of_tca6507_leds_match[] = {
 	{ .compatible = "ti,tca6507", },
 	{},
 };