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/pfla02_defconfig b/configs/pfla02_defconfig
index 0a03854..67d3ddd 100644
--- a/configs/pfla02_defconfig
+++ b/configs/pfla02_defconfig
@@ -40,6 +40,7 @@
 CONFIG_DM=y
 CONFIG_FSL_ESDHC=y
 CONFIG_MTD=y
+CONFIG_MTD_DEVICE=y
 CONFIG_NAND=y
 CONFIG_NAND_MXS=y
 CONFIG_SPI_FLASH=y