iio: adc: max1118: 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/max1118.c

@@ -71,7 +71,10 @@ static int max1118_read(struct spi_device *spi, int channel)
 		 */
 		{
 			.len = 0,
-			.delay_usecs = 1,	/* > CNVST Low Time 100 ns */
+			.delay = {	/* > CNVST Low Time 100 ns */
+				.value = 1,
+				.unit = SPI_DELAY_UNIT_USECS
+			},
 			.cs_change = 1,
 		},
 		/*
@@ -81,7 +84,10 @@ static int max1118_read(struct spi_device *spi, int channel)
 		 */
 		{
 			.len = 0,
-			.delay_usecs = 8,
+			.delay = {
+				.value = 8,
+				.unit = SPI_DELAY_UNIT_USECS
+			},
 		},
 		{
 			.rx_buf = &adc->data,