iio:dac:lpc18xx_dac: Swap from of* to mod_devicetable.h

This driver never used anything from the of specific headers.
mod_devicetable.h provides the struct of_device_id definition.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

drivers/iio/dac/lpc18xx_dac.c

@@ -16,9 +16,8 @@
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
+#include <linux/mod_devicetable.h>
 #include <linux/mutex.h>
-#include <linux/of.h>
-#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>