kconfig: make parent directories for the saved .config as needed

With menuconfig / nconfig, users can input any file path from the
"Save" menu, but it fails if the parent directory does not exist.

Why not create the parent directory automatically. I think this is
a user-friendly behavior.

I changed the error messages in menuconfig / nconfig.

"Nonexistent directory" is no longer the most likely reason of the
failure. Perhaps, the user specified the existing directory, or
attempted to write to the location without write permission.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/confdata.c

@@ -881,6 +881,9 @@ int conf_write(const char *name)
 		return -1;
 	}
 
+	if (make_parent_dir(name))
+		return -1;
+
 	env = getenv("KCONFIG_OVERWRITECONFIG");
 	if (env && *env) {
 		*tmpname = 0;

scripts/kconfig/mconf.c

@@ -936,7 +936,7 @@ static void conf_save(void)
 				set_config_filename(dialog_input_result);
 				return;
 			}
-			show_textbox(NULL, "Can't create file!  Probably a nonexistent directory.", 5, 60);
+			show_textbox(NULL, "Can't create file!", 5, 60);
 			break;
 		case 1:
 			show_helptext("Save Alternate Configuration", save_config_help);

scripts/kconfig/nconf.c

@@ -1438,8 +1438,7 @@ static void conf_save(void)
 				set_config_filename(dialog_input_result);
 				return;
 			}
-			btn_dialog(main_window, "Can't create file! "
-				"Probably a nonexistent directory.",
+			btn_dialog(main_window, "Can't create file!",
 				1, "<OK>");
 			break;
 		case 1: