iavf: delete the iavf client interface

iavf: delete the iavf client interface

The iavf client interface was added in 2017 by commit ed0e894de7c1
("i40evf: add client interface"), but there have never been any in-tree
callers.

It's not useful for future development either. The Intel out-of-tree
iavf and irdma drivers instead use an auxiliary bus, which is a better
solution.

Remove the iavf client interface code. Also gone are the client_task
work and the client_lock mutex.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20231027175941.1340255-9-jacob.e.keller@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>