Convert CONFIG_NAND to Kconfig

This converts the following to Kconfig:
   CONFIG_NAND

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Sync up a few more, add imply's]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/rastaban_defconfig b/configs/rastaban_defconfig
index a6deb7d..7bbe4d9 100644
--- a/configs/rastaban_defconfig
+++ b/configs/rastaban_defconfig
@@ -53,6 +53,7 @@
 CONFIG_OF_EMBED=y
 CONFIG_DFU_NAND=y
 CONFIG_MMC_OMAP_HS=y
+CONFIG_NAND=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_MTD_UBI_FASTMAP=y