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/bitmain_antminer_s9_defconfig b/configs/bitmain_antminer_s9_defconfig
index f59c767..e7f473b 100644
--- a/configs/bitmain_antminer_s9_defconfig
+++ b/configs/bitmain_antminer_s9_defconfig
@@ -54,6 +54,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_ZYNQ=y
+CONFIG_MTD_DEVICE=y
 CONFIG_NAND=y
 CONFIG_NAND_ZYNQ=y
 CONFIG_NAND_ZYNQ_USE_BOOTLOADER1_TIMINGS=y