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/zynq_cse_nand_defconfig b/configs/zynq_cse_nand_defconfig
index eb7e574..5ac68a8 100644
--- a/configs/zynq_cse_nand_defconfig
+++ b/configs/zynq_cse_nand_defconfig
@@ -43,6 +43,7 @@
 # CONFIG_DM_DEVICE_REMOVE is not set
 CONFIG_SPL_DM_SEQ_ALIAS=y
 # CONFIG_MMC is not set
+CONFIG_MTD_DEVICE=y
 CONFIG_NAND=y
 CONFIG_NAND_ZYNQ=y
 # CONFIG_EFI_LOADER is not set