kconfig: Update config changed flag before calling callback

Prior to commit 5ee54659 ("kconfig: change sym_change_count to a
boolean flag"), the conf_updated flag was set to the new value *before*
calling the callback. xconfig's save action depends on this behaviour,
because xconfig calls conf_get_changed() directly from the callback and
now sees the old value, thus never enabling the save button or the
shortcut.

Restore the previous behaviour.

Fixes: 5ee54659 ("kconfig: change sym_change_count to a boolean flag")
Signed-off-by: Jurica Vukadin <jura@vukad.in>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/confdata.c

@@ -1226,10 +1226,12 @@ static void (*conf_changed_callback)(void);
 
 void conf_set_changed(bool val)
 {
-	if (conf_changed_callback && conf_changed != val)
-		conf_changed_callback();
+	bool changed = conf_changed != val;
 
 	conf_changed = val;
+
+	if (conf_changed_callback && changed)
+		conf_changed_callback();
 }
 
 bool conf_get_changed(void)