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/tuxx1_defconfig b/configs/tuxx1_defconfig
index d3b9ca2..3e45802 100644
--- a/configs/tuxx1_defconfig
+++ b/configs/tuxx1_defconfig
@@ -29,6 +29,7 @@
 CONFIG_SYS_BOOTCOUNT_ADDR=0xE0113FF8
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_MTD_DEVICE=y
 # CONFIG_PCI is not set
 CONFIG_SYS_NS16550=y
 CONFIG_OF_LIBFDT=y