iio: adc: ti-tlc4541: Use new structure for SPI transfer delays

In a recent change to the SPI subsystem [1], a new `delay` struct was added
to replace the `delay_usecs`. This change replaces the current
`delay_usecs` with `delay` for this driver.

The `spi_transfer_delay_exec()` function [in the SPI framework] makes sure
that both `delay_usecs` & `delay` are used (in this order to preserve
backwards compatibility).

[1] commit bebcfd27 ("spi: introduce `delay` field for
`spi_transfer` + spi_transfer_delay_exec()")
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ti-tlc4541.c

@@ -189,7 +189,8 @@ static int tlc4541_probe(struct spi_device *spi)
 	/* Setup default message */
 	st->scan_single_xfer[0].rx_buf = &st->rx_buf[0];
 	st->scan_single_xfer[0].len = 3;
-	st->scan_single_xfer[1].delay_usecs = 3;
+	st->scan_single_xfer[1].delay.value = 3;
+	st->scan_single_xfer[1].delay.unit = SPI_DELAY_UNIT_NSECS;
 	st->scan_single_xfer[2].rx_buf = &st->rx_buf[0];
 	st->scan_single_xfer[2].len = 2;