This change adds the messaging support needed to support PTP.  In the case
of Tx timestamps it is necessary for the Switch Management entity to return
the frames via the mailbox as the host interface cannot know which port the
timestamp will be delivered to.  In addition there is only one clock on the
entire switch, as such the entity that has BAR 4 access is the only one who
can actually update the frequency as it is the only one with access.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>