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/k2g_evm_defconfig b/configs/k2g_evm_defconfig
index 911618c..0309c5f 100644
--- a/configs/k2g_evm_defconfig
+++ b/configs/k2g_evm_defconfig
@@ -38,6 +38,7 @@
 CONFIG_MMC_OMAP_HS=y
 CONFIG_NAND=y
 CONFIG_NAND_DAVINCI=y
+CONFIG_MTD_DEVICE=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_BAR=y