spi: Fix self assignment issue with ancillary->mode

There is an assignment of ancillary->mode to itself which looks
dubious since the proceeding comment states that the speed and
mode is taken over from the SPI main device, indicating that
ancillary->mode should assigned using the value spi->mode.
Fix this.

Addresses-Coverity: ("Self assignment")
Fixes: 0c79378c ("spi: add ancillary device support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210623172300.161484-1-colin.king@canonical.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -2183,7 +2183,7 @@ struct spi_device *spi_new_ancillary_device(struct spi_device *spi,
 
 	/* Take over SPI mode/speed from SPI main device */
 	ancillary->max_speed_hz = spi->max_speed_hz;
-	ancillary->mode = ancillary->mode;
+	ancillary->mode = spi->mode;
 
 	/* Register the new device */
 	rc = spi_add_device_locked(ancillary);