mtd: rawnand: denali_dt: use UCLASS_MTD instead of UCLASS_MISC

UCLASS_MTD is a better fit for NAND drivers.

Make NAND_DENALI_DT depend on DM_MTD, which is needed to compile
drivers/mtd/mtd-uclass.c

Also, make ARCH_UNIPHIER select DM_MTD because all the defconfig
of this platform enables NAND_DENALI_DT.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
index 7814d84..23201ca 100644
--- a/drivers/mtd/nand/raw/Kconfig
+++ b/drivers/mtd/nand/raw/Kconfig
@@ -116,7 +116,7 @@
 config NAND_DENALI_DT
 	bool "Support Denali NAND controller as a DT device"
 	select NAND_DENALI
-	depends on OF_CONTROL && DM
+	depends on OF_CONTROL && DM_MTD
 	help
 	  Enable the driver for NAND flash on platforms using a Denali NAND
 	  controller as a DT device.