tcp_comp: Fix ZSTD_decompressStream failed

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I48H9Z?from=project-issue


CVE: NA

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This patch fixes possible ZSTD_decompressStream failures. When decompressing
skb->data, should skip the previous rxm->offset data.

Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>