Convert CONFIG_MTD_PARTITIONS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_MTD_PARTITIONS
   CONFIG_MTD_DEVICE

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/vct_premium_onenand_defconfig b/configs/vct_premium_onenand_defconfig
index 523ea48..c7c6142 100644
--- a/configs/vct_premium_onenand_defconfig
+++ b/configs/vct_premium_onenand_defconfig
@@ -22,6 +22,7 @@
 CONFIG_CMD_UBI=y
 # CONFIG_CMD_UBIFS is not set
 CONFIG_ENV_IS_IN_ONENAND=y
+CONFIG_MTD_DEVICE=y
 CONFIG_NETDEVICES=y
 CONFIG_SMC911X=y
 CONFIG_SMC911X_BASE=0x00000000