net/mlx5: DR, Add function that tells if STE miss addr has been initialized

Up until now miss address in all the STEs was used to connect miss lists
and to link the last STE in the list to end anchor.
Match range STE will require special handling because its miss address is
part of the 'action'. That is, range action has hit and miss addresses.
Since the range action is always the last action, need to make sure that
its miss address isn't overwritten by the end anchor.

Adding new function mlx5dr_ste_is_miss_addr_set() to answer the question
whether the STE's miss address has already been set as part of STE
initialization. Use a callback that always returns false right now. Once
match range is added, a different callback will be used for that STE type.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Erez Shitrit <erezsh@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>