bootstash: Do not provide a default address for all

A valid memory location to stash bootstage information at will be
architecture dependent. Move the existing defaults to the main Kconfig
file for this option and set 0x0 as the default only for sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

common/bootstage.c

@@ -500,6 +500,7 @@ int bootstage_unstash(const void *base, int size)
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_BOOTSTAGE_STASH)
 int _bootstage_stash_default(void)
 {
 	return bootstage_stash(map_sysmem(CONFIG_BOOTSTAGE_STASH_ADDR, 0),
@@ -513,6 +514,7 @@ int _bootstage_unstash_default(void)
 
 	return bootstage_unstash(stash, CONFIG_BOOTSTAGE_STASH_SIZE);
 }
+#endif
 
 int bootstage_get_size(void)
 {