kconfig: require the argument of --defconfig

Currently, the argument for --defconfig is optional. If the argument
is not passed, the hard-coded default arch/$(ARCH)/defconfig is used.

It no longer happens in Linux since the last users of the default are
gone by the following commits:

- Commit f3e20ad67b ("s390: move arch/s390/defconfig to
  arch/s390/configs/defconfig")

- Commit 986a13769c ("alpha: move arch/alpha/defconfig to
  arch/alpha/configs/defconfig")

I want to kill the Linux-specific directory path embedded in the
Kconfig binary.

The --savedefconfig (reverse operation of --defconfig) requires an
argument, so it should not hurt to do likewise for --defconfig.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/conf.c

@@ -451,7 +451,7 @@ static struct option long_opts[] = {
 	{"oldaskconfig",    no_argument,       NULL, oldaskconfig},
 	{"oldconfig",       no_argument,       NULL, oldconfig},
 	{"syncconfig",      no_argument,       NULL, syncconfig},
-	{"defconfig",       optional_argument, NULL, defconfig},
+	{"defconfig",       required_argument, NULL, defconfig},
 	{"savedefconfig",   required_argument, NULL, savedefconfig},
 	{"allnoconfig",     no_argument,       NULL, allnoconfig},
 	{"allyesconfig",    no_argument,       NULL, allyesconfig},
@@ -562,8 +562,6 @@ int main(int ac, char **av)
 
 	switch (input_mode) {
 	case defconfig:
-		if (!defconfig_file)
-			defconfig_file = conf_get_default_confname();
 		if (conf_read(defconfig_file)) {
 			fprintf(stderr,
 				"***\n"