nfc: s3fwrn5: mark OF device ID tables as maybe unused

The driver can match either via OF or I2C ID tables.  If OF is disabled,
the table will be unused:

    drivers/nfc/s3fwrn5/i2c.c:265:34: warning:
        ‘of_s3fwrn5_i2c_match’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210528124200.79655-8-krzysztof.kozlowski@canonical.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/nfc/s3fwrn5/i2c.c

@@ -262,7 +262,7 @@ static const struct i2c_device_id s3fwrn5_i2c_id_table[] = {
 };
 MODULE_DEVICE_TABLE(i2c, s3fwrn5_i2c_id_table);
 
-static const struct of_device_id of_s3fwrn5_i2c_match[] = {
+static const struct of_device_id of_s3fwrn5_i2c_match[] __maybe_unused = {
 	{ .compatible = "samsung,s3fwrn5-i2c", },
 	{}
 };