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/socfpga_arria10_defconfig b/configs/socfpga_arria10_defconfig
index f3fea51..4278bd0 100644
--- a/configs/socfpga_arria10_defconfig
+++ b/configs/socfpga_arria10_defconfig
@@ -32,5 +32,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DWAPB_GPIO=y
 CONFIG_DM_MMC=y
+CONFIG_MTD_DEVICE=y
+CONFIG_MTD_PARTITIONS=y
 CONFIG_SPI=y
 CONFIG_USE_TINY_PRINTF=y