sfc: Enable RX scatter for flows steered by RFS

[ Upstream commit 7aa0076c497d6f0d5d957b431d0d80e1e9780274 ]

Received packets are only scattered if this is enabled in both the
matching filter and the receiving queue.  This was not being done for
filters inserted for RFS, so any packet requiring more than a single
descriptor was dropped.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>