iio: xilinx-xadc-core: Use local variable in xadc_read_raw

Minor cleanup: bit is already defined as chan->scan_type.realbits,
use bit when needed.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20211104082413.3681212-13-gwendal@chromium.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/xilinx-xadc-core.c

@@ -944,7 +944,7 @@ static int xadc_read_raw(struct iio_dev *indio_dev,
 				*val = 1000;
 				break;
 			}
-			*val2 = chan->scan_type.realbits;
+			*val2 = bits;
 			return IIO_VAL_FRACTIONAL_LOG2;
 		case IIO_TEMP:
 			/* Temp in C = (val * 503.975) / 2**bits - 273.15 */