ena: hide sysctl nodes for unused ENA queues
IO queue related attributes are registered statically at driver attach
with the rest of the ENA specific sysctl nodes. However, the number of
queues can be changed at runtime via the ena_sysctl_io_queues_nb
request, leading to a potential exposure of attributes for non-existing
queues.
Introduce a new ena_sysctl_update_queue_node_nb function, which
updates the sysctl nodes after the number of queues is altered.
This happens by either registering or unregistering node specific oids,
based on a delta between the previous and current queue count.
NOTE: All unregistered oids must be registered again before the driver
detach, e.g. by another call to this function.
Submitted by: Artur Rojek <ar@semihalf.com>
Obtained from: Semihalf
MFC after: 2 weeks
Sponsored by: Amazon, Inc.