spi: spi-loopback-test: use new `delay` field

This change replaces the use of the `delay_usecs` field with the new
`delay` field. The code/test still uses micro-seconds, but they are now
configured and used via the `struct spi_delay` format of the `delay` field.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20190926105147.7839-13-alexandru.ardelean@analog.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-loopback-test.c

@@ -298,12 +298,18 @@ static struct spi_test spi_tests[] = {
 			{
 				.tx_buf = TX(0),
 				.rx_buf = RX(0),
-				.delay_usecs = 1000,
+				.delay = {
+					.value = 1000,
+					.unit = SPI_DELAY_UNIT_USECS,
+				},
 			},
 			{
 				.tx_buf = TX(0),
 				.rx_buf = RX(0),
-				.delay_usecs = 1000,
+				.delay = {
+					.value = 1000,
+					.unit = SPI_DELAY_UNIT_USECS,
+				},
 			},
 		},
 	},
@@ -537,7 +543,7 @@ static int spi_test_check_elapsed_time(struct spi_device *spi,
 		unsigned long long nbits = (unsigned long long)BITS_PER_BYTE *
 					   xfer->len;
 
-		delay_usecs += xfer->delay_usecs;
+		delay_usecs += xfer->delay.value;
 		if (!xfer->speed_hz)
 			continue;
 		estimated_time += div_u64(nbits * NSEC_PER_SEC, xfer->speed_hz);