Convert CONFIG_DAVINCI_SPI to Kconfig

This converts the following to Kconfig:
   CONFIG_DAVINCI_SPI

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 494639f..5e31ee4 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -217,6 +217,12 @@
 	  used to access the SPI flash on AE3XX and AE250 platforms embedding
 	  this Andestech IP core.
 
+config DAVINCI_SPI
+	bool "Davinci & Keystone SPI driver"
+	depends on ARCH_DAVINCI || ARCH_KEYSTONE
+	help
+	  Enable the Davinci SPI driver
+
 config TI_QSPI
 	bool "TI QSPI driver"
 	help