CVE-2026-98792: netfilter: flowtable: generalize pending status bit

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

netfilter: flowtable: generalize pending status bit

Rename NFFLOWHWPENDING to NFFLOWPENDING and use it to inhibit the flowtable GC worker until pending hw offload work has been completed.

Apparently, nfflowoffloadstats() can schedule work to retrieve stats while the flow is being removed by GC.

And this bit can also be used in a follow up patch to disable GC until the flow has been fully added in both directions.

Revert the reordering done in commit d644b23afe1e ("netfilter: flowtable: publish HWDEAD after worker is done") to prevent a race between GC and hw offload handler.