CVE-2024-49938

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

wifi: ath9khtc: Use _skbsetlength() for resetting urb before resubmit

Syzbot points out that skbtrim() has a sanity check on the existing length of the skb, which can be uninitialised in some error paths. The intent here is clearly just to reset the length to zero before resubmitting, so switch to calling _skbsetlength(skb, 0) directly. In addition, _skbsetlength() already contains a call to skbresettailpointer(), so remove the redundant call.

The syzbot report came from ath9khifusbregincb(), but there's a similar usage of skbtrim() in ath9khifusbrxcb(), change both while we're at it.