spi: orion: use new `word_delay` field for SPI transfers

The `word_delay` field had it's type changed to `struct spi_delay`.
This allows users to specify nano-second or clock-cycle delays (if needed).

Converting to use `word_delay` is straightforward: it just uses the new
`spi_delay_exec()` routine, that handles the `unit` part.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20190926105147.7839-6-alexandru.ardelean@analog.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-orion.c

@@ -467,8 +467,7 @@ orion_spi_write_read(struct spi_device *spi, struct spi_transfer *xfer)
 			if (orion_spi_write_read_8bit(spi, &tx, &rx) < 0)
 				goto out;
 			count--;
-			if (xfer->word_delay_usecs)
-				udelay(xfer->word_delay_usecs);
+			spi_delay_exec(&xfer->word_delay, xfer);
 		} while (count);
 	} else if (word_len == 16) {
 		const u16 *tx = xfer->tx_buf;
@@ -478,8 +477,7 @@ orion_spi_write_read(struct spi_device *spi, struct spi_transfer *xfer)
 			if (orion_spi_write_read_16bit(spi, &tx, &rx) < 0)
 				goto out;
 			count -= 2;
-			if (xfer->word_delay_usecs)
-				udelay(xfer->word_delay_usecs);
+			spi_delay_exec(&xfer->word_delay, xfer);
 		} while (count);
 	}