eth: fbnic: unlink NAPIs from queues on error to open

CI hit a UaF in fbnic in the AF_XDP portion of the queues.py test.
The UaF is in the __sk_mark_napi_id_once() call in xsk_bind(),
NAPI has been freed. Looks like the device failed to open earlier,
and we lack clearing the NAPI pointer from the queue.

Fixes: 557d0223 ("eth: fbnic: centralize the queue count and NAPI<>queue setting")
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250728163129.117360-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>