spi: add support for DLN-2 USB-SPI adapter

This adds support for Diolan DLN2 USB-SPI adapter.

Information about the USB protocol interface can be found in the
Programmer's Reference Manual [1], see section 5.4.6 for the SPI
master module commands and responses.

[1] https://www.diolan.com/downloads/dln-api-manual.pdf

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 9982998..f60f37c 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -185,6 +185,16 @@
 	help
 	  SPI master controller for DaVinci/DA8x/OMAP-L/AM1x SPI modules.
 
+config SPI_DLN2
+       tristate "Diolan DLN-2 USB SPI adapter"
+       depends on MFD_DLN2
+       help
+         If you say yes to this option, support will be included for Diolan
+         DLN2, a USB to SPI interface.
+
+         This driver can also be built as a module.  If so, the module
+         will be called spi-dln2.
+
 config SPI_EFM32
 	tristate "EFM32 SPI controller"
 	depends on OF && ARM && (ARCH_EFM32 || COMPILE_TEST)