mtd: Add missing MTD dependency for cfi_mtd

cfi_mtd requires add_mtd_device() which is available only when MTD is
enabled that's why record this dependency.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/76ae01ce2b2c988758b69e0f0cdcc21bf301c01e.1688472227.git.michal.simek@amd.com
diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index 5fa88da..c56840c 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -128,7 +128,7 @@
 
 config FLASH_CFI_MTD
 	bool "Enable CFI MTD driver"
-	depends on FLASH_CFI_DRIVER
+	depends on FLASH_CFI_DRIVER && MTD
 	help
 	  This option enables the building of the cfi_mtd driver
 	  in the drivers directory. The driver exports CFI flash