gve: Add RSS cache for non RSS device option scenario

gve: Add RSS cache for non RSS device option scenario

Not all the devices have the capability for the driver to query for the
registered RSS configuration. The driver can discover this by checking
the relevant device option during setup. If it cannot, the driver needs
to store the RSS config cache and directly return such cache when
queried by the ethtool. RSS config is inited when driver probes. Also the
default RSS config will be adjusted when there is RX queue count change.

At this point, only keys of GVE_RSS_KEY_SIZE and indirection tables of
GVE_RSS_INDIR_SIZE are supported.

Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Praveen Kaligineedi <pkaligineedi@google.com>
Signed-off-by: Jeroen de Borst <jeroendb@google.com>
Link: https://patch.msgid.link/20250219200451.3348166-1-jeroendb@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>