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: NRavi Babu <ravibabu@ti.com>
Reviewed-by: NTom Rini <trini@konsulko.com>

common/spl/Kconfig

@@ -646,6 +646,7 @@ config SPL_USBETH_SUPPORT
 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