gpio: sim: actually use the OF module table

gpio: sim: actually use the OF module table

We don't assign the of_device_id table to the platform driver resulting
in the following build warning:

>> drivers/gpio/gpio-sim.c:388:34: warning: unused variable 'gpio_sim_of_match' [-Wunused-const-variable]
   static const struct of_device_id gpio_sim_of_match[] = {

This fixes it.

Fixes: 3f0279eb9e37 ("gpio: sim: new testing module")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>