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/MPC8313ERDB_NAND_66_defconfig b/configs/MPC8313ERDB_NAND_66_defconfig
index 2b75f92..f2600b7 100644
--- a/configs/MPC8313ERDB_NAND_66_defconfig
+++ b/configs/MPC8313ERDB_NAND_66_defconfig
@@ -5,7 +5,7 @@
 CONFIG_TARGET_MPC8313ERDB=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="SYS_66MHZ,NAND"
+CONFIG_SYS_EXTRA_OPTIONS="SYS_66MHZ"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_BOOTDELAY=6
 CONFIG_SPL=y
@@ -23,5 +23,6 @@
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_PHYLIB=y
+CONFIG_NAND=y
 CONFIG_SYS_NS16550=y
 CONFIG_OF_LIBFDT=y