net/sfc: allow to query RSS key and HF in isolated mode

net/sfc: allow to query RSS key and HF in isolated mode

Isolated mode prevents global RSS from being enabled and configured.
However, an application may need to query default RSS key and hash
functions when a flow rule with RSS action is added which does not
contain custom RSS key or hash function choice. In this case
global RSS key and hash functions will be used to handle the rule,
and there should be some way for the application to query these
global default settings to clarify expectations on the traffic
distribution.

Fixes: 84a9b48128c1 ("net/sfc: support flow API isolated mode")
Cc: stable@dpdk.org
Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>