regulator: 88pg86x: Fix W=1 build warning when CONFIG_OF=n

Fix below warning when CONFIG_OF=n:

drivers/regulator/88pg86x.c:87:34: warning: ‘pg86x_dt_ids’ defined but not used [-Wunused-const-variable=]
87 | static const struct of_device_id pg86x_dt_ids [] = {
   |                                  ^~~~~~~~~~~~

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20200821111210.0a0bed94@xhacker.debian
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/88pg86x.c

@@ -84,7 +84,7 @@ static int pg86x_i2c_probe(struct i2c_client *i2c)
 	return 0;
 }
 
-static const struct of_device_id pg86x_dt_ids [] = {
+static const struct of_device_id __maybe_unused pg86x_dt_ids[] = {
 	{ .compatible = "marvell,88pg867" },
 	{ .compatible = "marvell,88pg868" },
 	{ }