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>