fpga: altera-freeze-bridge: Address warning about unused variable

warning: unused variable 'altera_freeze_br_of_match'
 [-Wunused-const-variable]
  static const struct of_device_id altera_freeze_br_of_match[] = {

Fixes: ca24a648 ("fpga: add altera freeze bridge support")
Cc: Tom Rix <trix@redhat.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

drivers/fpga/altera-freeze-bridge.c

@@ -198,11 +198,13 @@ static const struct fpga_bridge_ops altera_freeze_br_br_ops = {
 	.enable_show = altera_freeze_br_enable_show,
 };
 
+#ifdef CONFIG_OF
 static const struct of_device_id altera_freeze_br_of_match[] = {
 	{ .compatible = "altr,freeze-bridge-controller", },
 	{},
 };
 MODULE_DEVICE_TABLE(of, altera_freeze_br_of_match);
+#endif
 
 static int altera_freeze_br_probe(struct platform_device *pdev)
 {