IPsec offloading callbacks may be called in atomic context, sleep is
not allowed in the implementation. Now use workqueue mechanism to
avoid this issue.

Extend existing workqueue mechanism for multicast configuration only
to universal use, so that all configuring through mailbox asynchronously
can utilize it.

Fixes: 859a497f ("nfp: implement xfrm callbacks and expose ipsec offload feature to upper layer")
Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>