xilinx_spi: add support for the DS570 IP.

This patch adds in support for the DS570 IP.

It's register compatible with the DS464, but adds support for 8/16/32 SPI.

The 8/16/32 support is added by attaching callbacks reading/writing the
proper amount of data. To indicate to the driver which amount of bits
to use a new field is introduced in the platform data struct.

Acked-by: Grant Likely <grant.likely@secretlab.ca>
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 b528271..4dda097 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -243,7 +243,7 @@
 	  SPI driver for Toshiba TXx9 MIPS SoCs
 
 config SPI_XILINX
-	tristate "Xilinx SPI controller"
+	tristate "Xilinx SPI controller common module"
 	depends on HAS_IOMEM && EXPERIMENTAL
 	select SPI_BITBANG
 	select SPI_XILINX_OF if (XILINX_VIRTEX || MICROBLAZE)
@@ -253,6 +253,8 @@
 	  See the "OPB Serial Peripheral Interface (SPI) (v1.00e)"
 	  Product Specification document (DS464) for hardware details.
 
+	  Or for the DS570, see "XPS Serial Peripheral Interface (SPI) (v2.00b)"
+
 config SPI_XILINX_OF
 	tristate "Xilinx SPI controller OF device"
 	depends on SPI_XILINX && (XILINX_VIRTEX || MICROBLAZE)