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/am335x_igep003x_defconfig b/configs/am335x_igep003x_defconfig
index 7ab2cb3..464f53f 100644
--- a/configs/am335x_igep003x_defconfig
+++ b/configs/am335x_igep003x_defconfig
@@ -52,6 +52,7 @@
 CONFIG_ISO_PARTITION=y
 CONFIG_EFI_PARTITION=y
 CONFIG_MMC_OMAP_HS=y
+CONFIG_NAND=y
 CONFIG_MTD_UBI_FASTMAP=y
 CONFIG_PHYLIB=y
 CONFIG_SYS_NS16550=y