dpaa2: Perform bus_dma pre-write sync before enqueue operation
Without a proper synchronization payload of the egress TCP segments
can be corrupted as tuexen@ described in
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=292006#c31.
This patch is indirectly related to 292006 because a properly enabled
and announced support for the TX checksum offloading hides potentially
corrupted frame payload.
NOTE: Returned back with updated placeholders.
PR: 292006
Reported by: tuexen@
Reviewed by: tuexen@
Tested by: dsl@, tuexen@
Differential Revision: https://reviews.freebsd.org/D56144
MFC after: 3 days