[Why]
aux_payload should be the struct used inside dc to start
aux transactions.  This will allow the old aux interface
to be seamlessly replaced.

[How]
Add three fields to aux_payload: reply, mot, defer_delay
This will mean that aux_payload has all data required
to submit a request.  Shift dc_link to use this struct
Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>