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/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
index 06b2ff9..df4cbd5 100644
--- a/drivers/mtd/nand/raw/Kconfig
+++ b/drivers/mtd/nand/raw/Kconfig
@@ -233,7 +233,7 @@
 config NAND_ARASAN
 	bool "Configure Arasan Nand"
 	select SYS_NAND_SELF_INIT
-	select DM_MTD
+	depends on DM_MTD
 	imply CMD_NAND
 	help
 	  This enables Nand driver support for Arasan nand flash