staging: erofs: fix vle_decompressed_index_clusterofs

This patch adds error handing code, and fixes a missing
endian conversion in vle_decompressed_index_clusterofs.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>