octeontx2-pf: Add packet transmission support

This patch adds the packet transmission support.
For a given skb prepares send queue descriptors (SQEs) and pushes them
to HW. Here driver doesn't maintain it's own SQ rings, SQEs are pushed
to HW using a silicon specific operations called LMTST. From the
instuction HW derives the transmit queue number and queues the SQE to
that queue. These LMTST instructions are designed to avoid queue
maintenance in SW and lockless behavior ie when multiple cores are trying
to add SQEs to same queue then HW will takecare of serialization, no need
for SW to hold locks.

Also supports scatter/gather.

Co-developed-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>