kconfig: fix 'invalid option' for help option

scripts/kconfig/conf supports -? option to show the help message.
This is not wired up to Makefile, so nobody would notice this, but
it also shows 'invalid option' message.

  $ ./scripts/kconfig/conf -?
  ./scripts/kconfig/conf: invalid option -- '?'
  Usage: ./scripts/kconfig/conf [-s] [option] <kconfig-file>
  [option] is _one_ of the following:
    --listnewconfig         List new options
    --helpnewconfig         List new options and help text
    --oldaskconfig          Start a new configuration using a line-oriented program
    ...

The reason is the '?' is missing in the short option list passed to
getopt_long().

While I fixed this issue, I also changed the option '?' to 'h'.
I prefer -h (or --help, if a long option is also desired).
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/conf.c

@@ -494,7 +494,7 @@ int main(int ac, char **av)
 
 	tty_stdio = isatty(0) && isatty(1);
 
-	while ((opt = getopt_long(ac, av, "s", long_opts, NULL)) != -1) {
+	while ((opt = getopt_long(ac, av, "hs", long_opts, NULL)) != -1) {
 		if (opt == 's') {
 			conf_set_message_callback(NULL);
 			continue;
@@ -550,7 +550,7 @@ int main(int ac, char **av)
 		case yes2modconfig:
 		case mod2yesconfig:
 			break;
-		case '?':
+		case 'h':
 			conf_usage(progname);
 			exit(1);
 			break;