sfc: move table locking into filter_table_{probe,remove} methods

We need to be able to drop the efx->filter_sem in ef100_filter_table_up()
 so that we can call functions that insert filters (and thus take that
 rwsem for read), which means the efx->type->filter_table_probe method
 needs to be responsible for taking the lock in the first place.

Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>