spi: Fix double "when"

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/linux/spi/spi.h

@@ -126,7 +126,7 @@ void spi_statistics_add_transfer_stats(struct spi_statistics *stats,
  *	for that name.  This appears in the sysfs "modalias" attribute
  *	for driver coldplugging, and in uevents used for hotplugging
  * @cs_gpio: gpio number of the chipselect line (optional, -ENOENT when
- *	when not using a GPIO line)
+ *	not using a GPIO line)
  *
  * @statistics: statistics for the spi_device
  *