octeontx2-af: Add support for runtime RSS algo index reservation

Introduced reserve_flowkey_alg_idx()to reserve RSS algorithm index,
it would internally use set_flowkey_fields() to generate fields
based on the flow key dynamically.

On AF driver init, it would reserve a predefined set RSS algo indexes,
which will be available all the time for all the AF driver consumers.
The leftover algo indexes can be reserved at runtime through
exiting nix_rss_flowkey_cfg mailbox message.

The NIX_FLOW_KEY_TYPE_PORT is removed from predefined a set of RSS flow
type as it is not used by any consumer.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>