Register move operation is encoded as alu no op.  This means
that one has to specify number of unused/none parameters to
the emit_alu().  Add a helper.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NSimon Horman <simon.horman@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>