xilinx_spi: add a platform driver using the xilinx_spi common module.

This patch adds in a platform device driver using the xilinx_spi common module.

Tested-by: John Linn <John.Linn@xilinx.com>
Signed-off-by: Richard Röjfors <richard.rojfors@mocean-labs.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 4dda097..c00f9e5 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -261,6 +261,13 @@
 	help
 	  This is the OF driver for the SPI controller IP from the Xilinx EDK.
 
+config SPI_XILINX_PLTFM
+	tristate "Xilinx SPI controller platform device"
+	depends on SPI_XILINX
+	help
+	  This is the platform driver for the SPI controller IP
+	  from the Xilinx EDK.
+
 #
 # Add new SPI master controllers in alphabetical order above this line
 #