sfc: add function to atomically update a rule in the MAE

efx_mae_update_rule() changes the action-set-list attached to an MAE
 flow rule in the Action Rule Table.
We will use this when neighbouring updates change encap actions.

Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>