kconfig: fix MODULES-related bug in case of no .config

There seems to be a kconfig bug due to MODULES not always being
evaluated if no .config is found. Take the following Kconfig as an
example:

config MODULES
	def_bool y

config FOO
	def_tristate m

With no .config, the following configuration is generated:

CONFIG_MODULES=y
CONFIG_FOO=y

With an empty .config, the following:

CONFIG_MODULES=y
CONFIG_FOO=m

Tristate choice statements can also exhibit the problem, due to having an
implicit rev_dep (select) containing "m".

The problem is that MODULES is never evaluted in conf_read_simple() unless
there's a .config. The following patch fixes this.
Signed-off-by: Ulf Magnusson <ulfalizer.lkml@gmail.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/confdata.c

@@ -170,8 +170,11 @@ int conf_read_simple(const char *name, int def)
 		if (in)
 			goto load;
 		sym_add_change_count(1);
-		if (!sym_defconfig_list)
+		if (!sym_defconfig_list) {
+			if (modules_sym)
+				sym_calc_value(modules_sym);
 			return 1;
+		}
 
 		for_all_defaults(sym_defconfig_list, prop) {
 			if (expr_calc_value(prop->visible.expr) == no ||