iio: accel: kxsd9: declare missing of table

Add missing <of_device_id> table for SPI driver relying on SPI
device match since compatible is in a DT binding or in a DTS.

Before this patch:
modinfo drivers/iio/accel/kxsd9-spi.ko  | grep alias
alias:          spi:kxsd9

After this patch:
modinfo drivers/iio/accel/kxsd9-spi.ko  | grep alias
alias:          spi:kxsd9
alias:          of:N*T*Ckionix,kxsd9C*
alias:          of:N*T*Ckionix,kxsd9
Reported-by: Javier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: Daniel Gomez <dagmcr@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/kxsd9-spi.c

 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/spi/spi.h>
 #include <linux/module.h>
 #include <linux/slab.h>
@@ -40,10 +42,17 @@ static const struct spi_device_id kxsd9_spi_id[] = {
 };
 MODULE_DEVICE_TABLE(spi, kxsd9_spi_id);
 
+static const struct of_device_id kxsd9_of_match[] = {
+        { .compatible = "kionix,kxsd9" },
+        { },
+};
+MODULE_DEVICE_TABLE(of, kxsd9_of_match);
+
 static struct spi_driver kxsd9_spi_driver = {
 	.driver = {
 		.name = "kxsd9",
 		.pm = &kxsd9_dev_pm_ops,
+		.of_match_table = kxsd9_of_match,
 	},
 	.probe = kxsd9_spi_probe,
 	.remove = kxsd9_spi_remove,