regulator: lp872x: Mark OF related data as maybe unused

The driver can be compile tested with !CONFIG_OF making certain data
unused:

  drivers/regulator/lp872x.c:931:34: error: ‘lp872x_dt_ids’ defined but not used [-Werror=unused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230310214553.275450-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/lp872x.c

@@ -927,7 +927,7 @@ static int lp872x_probe(struct i2c_client *cl)
 	return lp872x_regulator_register(lp);
 }
 
-static const struct of_device_id lp872x_dt_ids[] = {
+static const struct of_device_id lp872x_dt_ids[] __maybe_unused = {
 	{ .compatible = "ti,lp8720", },
 	{ .compatible = "ti,lp8725", },
 	{ }