mtd: ensure CMD_NAND is compiled when its options are selected

In some files, options of CMD_NAND are selected but not the command
itself. Fix this inconsistency.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
diff --git a/configs/m53menlo_defconfig b/configs/m53menlo_defconfig
index dde3f40..62becff 100644
--- a/configs/m53menlo_defconfig
+++ b/configs/m53menlo_defconfig
@@ -37,6 +37,7 @@
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
+CONFIG_CMD_NAND=y
 CONFIG_CMD_NAND_TRIMFFS=y
 # CONFIG_CMD_PINMUX is not set
 CONFIG_CMD_USB=y