fpga: xilinx-pr-decoupler: Address warning about unused variable

warning: ‘xlnx_pr_decoupler_of_match’ defined but not used
 [-Wunused-const-variable=]
 static const struct of_device_id xlnx_pr_decoupler_of_match[] = {

Fixes: 7e961c12 ("fpga: Add support for Xilinx LogiCORE PR Decoupler")
Cc: Tom Rix <trix@redhat.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

drivers/fpga/xilinx-pr-decoupler.c

@@ -81,6 +81,7 @@ static const struct fpga_bridge_ops xlnx_pr_decoupler_br_ops = {
 	.enable_show = xlnx_pr_decoupler_enable_show,
 };
 
+#ifdef CONFIG_OF
 static const struct xlnx_config_data decoupler_config = {
 	.name = "Xilinx PR Decoupler",
 };
@@ -99,6 +100,7 @@ static const struct of_device_id xlnx_pr_decoupler_of_match[] = {
 	{},
 };
 MODULE_DEVICE_TABLE(of, xlnx_pr_decoupler_of_match);
+#endif
 
 static int xlnx_pr_decoupler_probe(struct platform_device *pdev)
 {