iavf: fix temporary deadlock and failure to set MAC address

We are seeing an issue where setting the MAC address on iavf fails with
EAGAIN after the 2.5s timeout expires in iavf_set_mac().

There is the following deadlock scenario:

iavf_set_mac(), holding rtnl_lock, waits on:
  iavf_watchdog_task (within iavf_wq) to send a message to the PF,
 and
  iavf_adminq_task (within iavf_wq) to receive a response from the PF.
In this adapter state (>=__IAVF_DOWN), these tasks do not need to take
rtnl_lock, but iavf_wq is a global single-threaded workqueue, so they
may get stuck waiting for another adapter's iavf_watchdog_task to run
iavf_init_config_adapter(), which does take rtnl_lock.

The deadlock resolves itself by the timeout in iavf_set_mac(),
which results in EAGAIN returned to userspace.

Let's break the deadlock loop by changing iavf_wq into a per-adapter
workqueue, so that one adapter's tasks are not blocked by another's.

Fixes: 35a2443d ("iavf: Add waiting for response from PF in set mac")
Co-developed-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>