nand: Kconfig: Change dependency for NAND_ARASAN

NAND_ARASAN selecting DM_MTD uunconditionally. Driver can be enabled with
!DM that's why Kconfig it showing it as error:

WARNING: unmet direct dependencies detected for DM_MTD
  Depends on [n]: DM [=n]
  Selected by [y]:
  - NAND_ARASAN [=y] && MTD_RAW_NAND [=y]

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xilinx_zynqmp_virt_defconfig b/configs/xilinx_zynqmp_virt_defconfig
index 23d7ddf..2f72d04 100644
--- a/configs/xilinx_zynqmp_virt_defconfig
+++ b/configs/xilinx_zynqmp_virt_defconfig
@@ -95,6 +95,7 @@
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_ZYNQ=y
 CONFIG_MTD=y
+CONFIG_DM_MTD=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_ARASAN=y
 CONFIG_SYS_NAND_MAX_CHIPS=2