spi:Add Freescale DSPI driver for Vybrid VF610 platform

The serial peripheral interface (SPI) module implemented on Freescale Vybrid
platform provides a synchronous serial bus for communication between Vybrid
and the external peripheral device.
The SPI supports full-duplex, three-wire synchronous transfer, has TX/RX FIFO
with depth of four entries.

This driver is the SPI master mode driver and has been tested on Vybrid
VF610TWR board.

Signed-off-by: Alison Wang <b18965@freescale.com>
Signed-off-by: Chao Fu  <b44548@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 89cbbab..b9da650 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -248,6 +248,13 @@
 	  This also enables using the Aeroflex Gaisler GRLIB SPI controller in
 	  master mode.
 
+config SPI_FSL_DSPI
+	tristate "Freescale DSPI controller"
+	select SPI_BITBANG
+	help
+	  This enables support for the Freescale DSPI controller in master
+	  mode. VF610 platform uses the controller.
+
 config SPI_FSL_ESPI
 	bool "Freescale eSPI controller"
 	depends on FSL_SOC