cmd: CONFIG_CMD_SAVES depends on CONFIG_CMD_LOADS

CONFIG_CMD_SAVES is used to enable support for the "saveenv" command
and is only implemented in cmd/load.c
when "#if defined(CONFIG_CMD_LOADS)" is met.

It is recommended to add dependency constraints to its definition.
Prevents "saveenv" command from not being supported
when "CONFIG_CMD_SAVES=y CONFIG_CMD_LOADS=n".

Suggested-by: Yanjie Ren <renyanjie01@gmail.com>
Signed-off-by: Ying Sun <sunying@nj.iscas.ac.cn>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd/Kconfig

@@ -1228,6 +1228,7 @@ config LOADS_ECHO
 
 config CMD_SAVES
 	bool "saves - Save a file over serial in S-Record format"
+	depends on CMD_LOADS
 	help
 	  Provides a way to save a binary file using the Motorola S-Record
 	  format over the serial line.