spi: correct the transfer_one_message documentation wording

The transfer_one_message callback handles messages, not transfers.
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Signed-off-by: NMark Brown <broonie@linaro.org>

Documentation/spi/spi-summary

@@ -543,7 +543,7 @@ SPI MASTER METHODS
 	queuing transfers that arrive in the meantime. When the driver is
 	finished with this message, it must call
 	spi_finalize_current_message() so the subsystem can issue the next
-	transfer. This may sleep.
+	message. This may sleep.
 
     master->transfer_one(struct spi_master *master, struct spi_device *spi,
 			 struct spi_transfer *transfer)

include/linux/spi/spi.h

@@ -273,7 +273,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  *	message while queuing transfers that arrive in the meantime. When the
  *	driver is finished with this message, it must call
  *	spi_finalize_current_message() so the subsystem can issue the next
- *	transfer
+ *	message
  * @unprepare_transfer_hardware: there are currently no more messages on the
  *	queue so the subsystem notifies the driver that it may relax the
  *	hardware by issuing this call