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_zc770_xm011_defconfig b/configs/zynq_zc770_xm011_defconfig
index af79f6e..1ec6ee4 100644
--- a/configs/zynq_zc770_xm011_defconfig
+++ b/configs/zynq_zc770_xm011_defconfig
@@ -36,6 +36,7 @@
 CONFIG_FPGA_ZYNQPL=y
 CONFIG_DM_GPIO=y
 # CONFIG_MMC is not set
+CONFIG_MTD_DEVICE=y
 CONFIG_NAND=y
 CONFIG_NAND_ZYNQ=y
 CONFIG_DEBUG_UART_ZYNQ=y