[PATCH] spi: spi.h: add missing kernel-doc for @last_cs_index_mask

[Randy Dunlap <rdunlap@xxxxxxxxxxxxx>]

kernel-doc complains about last_cs_index_mask not described, so add its
decscription.

spi.h:778: warning: Function parameter or struct member 'last_cs_index_mask' not described in 'spi_controller'

Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
---
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Andy Shevchenko <andy@xxxxxxxxxx>
Cc: linux-spi@xxxxxxxxxxxxxxx

 include/linux/spi/spi.h |    1 +
 1 file changed, 1 insertion(+)

diff -- a/include/linux/spi/spi.h b/include/linux/spi/spi.h
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -453,6 +453,7 @@ extern struct spi_device *spi_new_ancill
  * @last_cs_mode_high: was (mode & SPI_CS_HIGH) true on the last call to set_cs.
  * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
  *           selected
+ * @last_cs_index_mask: bit mask the last chip selects that were used
  * @xfer_completion: used by core transfer_one_message()
  * @busy: message pump is busy
  * @running: message pump is running