iio: dac: mcp4821: Switch to including mod_devicetable.h for struct of_device_id definition.

of.h was only included for this definition, so include the correct header
instead.
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240218173323.1023703-9-jic23@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/mcp4821.c

@@ -17,7 +17,7 @@
  */
 
 #include <linux/module.h>
-#include <linux/of.h>
+#include <linux/mod_devicetable.h>
 #include <linux/spi/spi.h>
 
 #include <linux/iio/iio.h>