iio:adc:ad7476: Use GENMASK() macro

Signed-off-by: Peter Meerwald <[e-mail]>
Acked-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ad7476.c

···
 #include <linux/regulator/consumer.h>
 #include <linux/err.h>
 #include <linux/module.h>
+#include <linux/bitops.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
-
-#define RES_MASK(bits)	((1 << (bits)) - 1)
 
 struct ad7476_state;
 
···
 		if (ret < 0)
 			return ret;
 		*val = (ret >> st->chip_info->channel[0].scan_type.shift) &
-			RES_MASK(st->chip_info->channel[0].scan_type.realbits);
+			GENMASK(st->chip_info->channel[0].scan_type.realbits - 1, 0);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		if (!st->chip_info->int_vref_uv) {