CVE-2021-47017 ath10k: Fix a use after free in ath10k_htc_send_bundle

In the Linux kernel, the following vulnerability has been resolved:

ath10k: Fix a use after free in ath10k_htc_send_bundle

In ath10k_htc_send_bundle, the bundle_skb could be freed by
dev_kfree_skb_any(bundle_skb). But the bundle_skb is used later
by bundle_skb->len.

As skb_len = bundle_skb->len, my patch replaces bundle_skb->len to
skb_len after the bundle_skb was freed.