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/configs/omapl138_lcdk_defconfig b/configs/omapl138_lcdk_defconfig
index 0d4506e..944be2b 100644
--- a/configs/omapl138_lcdk_defconfig
+++ b/configs/omapl138_lcdk_defconfig
@@ -36,4 +36,5 @@
 CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_SYS_NS16550=y
+CONFIG_DAVINCI_SPI=y
 CONFIG_OF_LIBFDT=y