Convert CONFIG_NAND_DAVINCI to Kconfig

This converts the following to Kconfig:
   CONFIG_NAND_DAVINCI

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/ipam390_defconfig b/configs/ipam390_defconfig
index 15c4944..d1a6e54 100644
--- a/configs/ipam390_defconfig
+++ b/configs/ipam390_defconfig
@@ -34,4 +34,6 @@
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_NAND=y
 # CONFIG_MMC is not set
+CONFIG_NAND=y
+CONFIG_NAND_DAVINCI=y
 CONFIG_SYS_NS16550=y