nfp: flower: remove list infastructure from MAC offload

Potential MAC destination addresses for tunnel end-points are offloaded to
firmware. This was done by building a list of such MACs and writing to
firmware as blocks of addresses.

Simplify this code by removing the list format and sending a new message
for each offloaded MAC.

This is in preparation for delete MAC messages. There will be one delete
flag per message so we cannot assume that this applies to all addresses
in a list.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>