mtd: atmel_nand: fix the warning when CONFIG_OF is not defined

This patch fix following warning:

drivers/mtd/nand/atmel_nand.c:2007: warning: 'atmel_nand_nfc_match' defined but not used

This patch add '#if defined(CONFIG_OF)' block to guard around the definition
of atmel_nand_nfc_match, in order to avoid the warning when the kernel is
configured without DT support.
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/atmel_nand.c

@@ -2251,10 +2251,12 @@ static int atmel_nand_nfc_probe(struct platform_device *pdev)
 	return 0;
 }
 
+#if defined(CONFIG_OF)
 static struct of_device_id atmel_nand_nfc_match[] = {
 	{ .compatible = "atmel,sama5d3-nfc" },
 	{ /* sentinel */ }
 };
+#endif
 
 static struct platform_driver atmel_nand_nfc_driver = {
 	.driver = {