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/spear320_defconfig b/configs/spear320_defconfig
index 001828d..5d31874 100644
--- a/configs/spear320_defconfig
+++ b/configs/spear320_defconfig
@@ -20,6 +20,8 @@
 CONFIG_SYS_I2C_DW=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_MTD_DEVICE=y
+CONFIG_MTD_PARTITIONS=y
 CONFIG_NETDEVICES=y
 CONFIG_PHY_GIGE=y
 CONFIG_ETH_DESIGNWARE=y