spl: Kconfig: dfu: spl-dfu depends on SPL_RAM_SUPPORT

Since SPL_DFU_SUPPORT is depends on SPL_RAM_SUPPORT,
hence select SPL_DFU_SUPPORT only when
SPL_RAM_SUPPORT is chosen.

Signed-off-by: Ravi Babu <ravibabu@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index ea6fbb6..1231351 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -646,6 +646,7 @@
 config SPL_DFU_SUPPORT
 	bool "Support DFU (Device Firmware Upgarde)"
 	select SPL_HASH_SUPPORT
+	depends on SPL_RAM_SUPPORT
 	help
 	  This feature enables the DFU (Device Firmware Upgarde) in SPL with
 	  RAM memory device support. The ROM code will load and execute