kconfig: remove unneeded menu_is_visible() call in conf_write_defconfig()

When the condition 'sym == NULL' is met, the code will reach the
'next_menu' label regardless of the return value from menu_is_visible().

menu_is_visible() calculates some symbol values as a side-effect, for
instance by calling expr_calc_value(menu->visibility), but all the
symbol values will be calculated eventually.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/confdata.c

@@ -799,10 +799,7 @@ int conf_write_defconfig(const char *filename)
 	while (menu != NULL)
 	{
 		sym = menu->sym;
-		if (sym == NULL) {
-			if (!menu_is_visible(menu))
-				goto next_menu;
-		} else if (!sym_is_choice(sym)) {
+		if (sym && !sym_is_choice(sym)) {
 			sym_calc_value(sym);
 			if (!(sym->flags & SYMBOL_WRITE))
 				goto next_menu;