CVE-2026-23054: net: hv_netvsc: reject RSS hash key programming without RX indirection table

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

net: hvnetvsc: reject RSS hash key programming without RX indirection table

RSS configuration requires a valid RX indirection table. When the device reports a single receive queue, rndisfilterdeviceadd() does not allocate an indirection table, accepting RSS hash key updates in this state leads to a hang.

Fix this by gating netvscsetrxfh() on ndc->rxtablesz and return -EOPNOTSUPP when the table is absent. This aligns setrxfh with the device capabilities and prevents incorrect behavior.