Add support to create flow rule that forward packets
to the first flow table in the next priority (next priority
could be the first priority in the next namespace or the
next priority in the same namespace).
This feature could be used for DONT_TRAP rules or rules
that only want to mark the packet with flow tag.

In order to do it optimally, each flow table has list
of all rules that point to this flow table,
when a flow table is destroyed/created, we update the list
head correspondingly.

This kind of rule is created when destination is NULL and
action is MLX5_FLOW_CONTEXT_ACTION_FWD_NEXT_PRIO.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>