xilinx_spi: Split into of driver and generic part.

This patch splits the xilinx_spi driver into a generic part and a
OF driver part.

The reason for this is to later add in a platform driver as well.

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 2a4ba19..f34a2d1 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -244,14 +244,21 @@
 
 config SPI_XILINX
 	tristate "Xilinx SPI controller"
-	depends on (XILINX_VIRTEX || MICROBLAZE) && EXPERIMENTAL
+	depends on EXPERIMENTAL
 	select SPI_BITBANG
+	select SPI_XILINX_OF if (XILINX_VIRTEX || MICROBLAZE)
 	help
 	  This exposes the SPI controller IP from the Xilinx EDK.
 
 	  See the "OPB Serial Peripheral Interface (SPI) (v1.00e)"
 	  Product Specification document (DS464) for hardware details.
 
+config SPI_XILINX_OF
+	tristate "Xilinx SPI controller OF device"
+	depends on SPI_XILINX && (XILINX_VIRTEX || MICROBLAZE)
+	help
+	  This is the OF driver for the SPI controller IP from the Xilinx EDK.
+
 #
 # Add new SPI master controllers in alphabetical order above this line
 #