kconfig: fix return code for invalid boolean symbol in conf_set_sym_val()

Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>

scripts/kconfig/confdata.c

@@ -141,7 +141,7 @@ static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
 			break;
 		}
 		conf_warning("symbol value '%s' invalid for %s", p, sym->name);
-		break;
+		return 1;
 	case S_OTHER:
 		if (*p != '"') {
 			for (p2 = p; *p2 && !isspace(*p2); p2++)